[chore] Removed $ from command for contribution guidance (#3114)

The copy in markdown file always copy the $ as well when copying the command,
I need to remove the $ manually each time.

Co-authored-by: Leighton Chen <[email protected]>
Co-authored-by: Riccardo Magliocchetti <[email protected]>

Author: 3 people

CONTRIBUTING.md

@@ -56,7 +56,7 @@ some aspects of development, including testing against multiple Python versions.
 To install `tox`, run:
 
 ```sh
-$ pip install tox
+pip install tox
 ```
 
 You can run `tox` with the following arguments:
@@ -74,13 +74,13 @@ You can run `tox` with the following arguments:
 `ruff check` and `ruff format` are executed when `tox -e ruff` is run. We strongly recommend you to configure [pre-commit](https://pre-commit.com/) locally to run `ruff` automatically before each commit by installing it as git hooks. You just need to [install pre-commit](https://pre-commit.com/#install) in your environment:
 
 ```console
-$ pip install pre-commit -c dev-requirements.txt
+pip install pre-commit -c dev-requirements.txt
 ```
 
 and run this command inside the git repository:
 
 ```console
-$ pre-commit install
+pre-commit install
 ```
 
 See
@@ -126,31 +126,45 @@ pull requests (PRs).
 To create a new PR, fork the project in GitHub and clone the upstream repo:
 
 ```sh
-$ git clone https://github.com/open-telemetry/opentelemetry-python-contrib.git
-$ cd opentelemetry-python-contrib
+git clone https://github.com/open-telemetry/opentelemetry-python-contrib.git
+cd opentelemetry-python-contrib
 ```
 
 Add your fork as an origin:
 
 ```sh
-$ git remote add fork https://github.com/YOUR_GITHUB_USERNAME/opentelemetry-python-contrib.git
+git remote add fork https://github.com/YOUR_GITHUB_USERNAME/opentelemetry-python-contrib.git
 ```
 
-Run tests:
+make sure you have all supported versions of Python installed, install `tox` only for the first time:
 
 ```sh
-# make sure you have all supported versions of Python installed
-$ pip install tox  # only first time.
-$ tox  # execute in the root of the repository
+pip install tox
+```
+
+Run tests in the root of the repository (this will run all tox environments and may take some time):
+
+```sh
+tox
 ```
 
 Check out a new branch, make modifications and push the branch to your fork:
 
 ```sh
-$ git checkout -b feature
-# edit files
-$ git commit
-$ git push fork feature
+git checkout -b feature
+```
+
+After you edit the files, stage changes in the current directory:
+
+```sh
+git add .
+```
+
+Then run the following to commit the changes:
+
+```sh
+git commit
+git push fork feature
 ```
 
 Open a pull request against the main `opentelemetry-python-contrib` repo.