ci: pin setuptools (#4085) (#4087)

## Description

The latest release of setuptools has broken support for editable installs, which is what riot does. See
pypa/setuptools#3504 for more details.

## Checklist
- [x] Title must conform to [conventional commit](https://github.com/conventional-changelog/commitlint/tree/master/%40commitlint/config-conventional).
- [x] Add additional sections for `feat` and `fix` pull requests.
- [x] Ensure tests are passing for affected code.
- [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.

## Reviewer Checklist
- [ ] Title is accurate.
- [ ] Description motivates each change.
- [ ] No unnecessary changes were introduced in this PR.
- [ ] PR cannot be broken up into smaller PRs.
- [ ] 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.
- [x] Release note has been added for fixes and features, or else `changelog/no-changelog` label added.
- [ ] All relevant GitHub issues are correctly linked.
- [ ] Backports are identified and tagged with Mergifyio.
- [ ] Add to milestone.

(cherry picked from commit 1aff4d5)

Co-authored-by: Gabriele N. Tornetta <[email protected]>

Author: mergify[bot]

pyproject.toml

@@ -1,5 +1,5 @@
 [build-system]
-requires = ["setuptools >= 40.6.0", "setuptools_scm[toml] >=4,<6.1", "cython", "cmake >= 3.14", "ninja"]
+requires = ["setuptools >= 40.6.0,<64", "setuptools_scm[toml] >=4,<6.1", "cython", "cmake >= 3.14", "ninja"]
 build-backend = "setuptools.build_meta"
 
 [tool.setuptools_scm]