fix(starlette framework tests): unpin sqlalchemy [backport #4801 to 1.6] (#4806)

## Description
The starlette framework tests currently pin sqlalchemy to 1.4.41 due to
an upstream issue which has now closed:
encode/databases#512. It looks like we can
unpin this dependency.

Note: this also indirectly fixes the failing starlette framework tests
due to this now closed upstream issue:
encode/databases#513, where sqlalchemy==1.4.42
added a new private field in the SQLAlchemy cursor class. While this job
uses the latest databases package that has accounted for this field,
this was causing attribute errors since we were using a previous version
of sqlalchemy that did not yet have that private field added.


<!-- If this is a breaking change, explain why it is necessary. Breaking
changes must append `!` after the type/scope. See
https://ddtrace.readthedocs.io/en/stable/contributing.html for more
details. -->

## Checklist
- [ ] Followed the [library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/contributing.html#Release-Note-Guidelines)
when writing a release note.
- [ ] Add additional sections for `feat` and `fix` pull requests.
- [ ] [Library
documentation](https://github.com/DataDog/dd-trace-py/tree/1.x/docs)
and/or [Datadog's documentation
site](https://github.com/DataDog/documentation/) is updated. Link to doc
PR in description.

<!-- Copy and paste the relevant snippet based on the type of pull
request -->

<!-- START feat -->

## Motivation
<!-- Expand on why the change is required, include relevant context for
reviewers -->

## Design 
<!-- Include benefits from the change as well as possible drawbacks and
trade-offs -->

## Testing strategy
<!-- Describe the automated tests and/or the steps for manual testing.

<!-- END feat -->

<!-- START fix -->

## Relevant issue(s)
<!-- Link the pull request to any issues related to the fix. Use
keywords for links to automate closing the issues once the pull request
is merged. -->

## Testing strategy
<!-- Describe any added regression tests and/or the manual testing
performed. -->

<!-- END fix -->

## Reviewer Checklist
- [x] Title is accurate.
- [x] Description motivates each change.
- [x] No unnecessary changes were introduced in this PR.
- [x] Avoid breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes unless absolutely necessary.
- [x] Tests provided or description of manual testing performed is
included in the code or PR.
- [x] Release note has been added and follows the [library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/contributing.html#Release-Note-Guidelines),
or else `changelog/no-changelog` label added.
- [x] All relevant GitHub issues are correctly linked.
- [x] Backports are identified and tagged with Mergifyio.

## Description
<!-- Briefly describe the change and why it was required. -->

<!-- If this is a breaking change, explain why it is necessary. Breaking
changes must append `!` after the type/scope. See
https://ddtrace.readthedocs.io/en/stable/contributing.html for more
details. -->

## Checklist
- [x] Followed the [library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/contributing.html#Release-Note-Guidelines)
when writing a release note.
- [x] Add additional sections for `feat` and `fix` pull requests.
- [x] [Library
documentation](https://github.com/DataDog/dd-trace-py/tree/1.x/docs)
and/or [Datadog's documentation
site](https://github.com/DataDog/documentation/) is updated. Link to doc
PR in description.

<!-- Copy and paste the relevant snippet based on the type of pull
request -->

<!-- START feat -->

## Motivation
<!-- Expand on why the change is required, include relevant context for
reviewers -->

## Design 
<!-- Include benefits from the change as well as possible drawbacks and
trade-offs -->

## Testing strategy
<!-- Describe the automated tests and/or the steps for manual testing.

<!-- END feat -->

<!-- START fix -->

## Relevant issue(s)
<!-- Link the pull request to any issues related to the fix. Use
keywords for links to automate closing the issues once the pull request
is merged. -->

## Testing strategy
<!-- Describe any added regression tests and/or the manual testing
performed. -->

<!-- END fix -->

## Reviewer Checklist
- [ ] Title is accurate.
- [ ] Description motivates each change.
- [ ] No unnecessary changes were introduced in this PR.
- [ ] Avoid breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes unless absolutely necessary.
- [ ] Tests provided or description of manual testing performed is
included in the code or PR.
- [ ] Release note has been added and follows the [library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/contributing.html#Release-Note-Guidelines),
or else `changelog/no-changelog` label added.
- [ ] All relevant GitHub issues are correctly linked.
- [ ] Backports are identified and tagged with Mergifyio.

Author: Yun-Kim

.github/workflows/test_frameworks.yml

@@ -309,9 +309,6 @@ jobs:
         run: pip install ../ddtrace
       - name: Install dependencies
         run: scripts/install
-      - name: Pin SQLAlchemy
-        # https://github.com/encode/databases/issues/512
-        run: pip install "SQLAlchemy==1.4.41"
       #Parameters for keyword expression skip 3 failing tests that are expected due to asserting on headers. The errors are because our context propagation headers are being added
       #test_staticfiles_with_invalid_dir_permissions_returns_401 fails with and without ddtrace enabled
       - name: Run tests