Update contributing.rst

[umutsoysal]

How to run .mystnb files are not clear so I am suggesting this sentence.

Description

Please provide a brief description of the changes made in this pull request.

Issue linked

Please mention the issue number or describe the problem this pull request addresses.

Checklist

• I have tested my changes locally.
• I have added necessary documentation or updated existing documentation.
• I have followed the coding style guidelines of this project.
• I have added appropriate unit tests.
• I have reviewed my changes before submitting this pull request.
• I have linked the issue or issues that are solved to the PR if any.
• I have assigned this PR to myself.
• I have added the minimum version decorator to any new backend method implemented.
• I have made sure that the title of my PR follows Conventional commits style (e.g. feat: extrude circle to cylinder)

[RobPasMue]

Hi @umutsoysal - thanks for opening the PR. However, since you are an Ansys employee, for legal reasons you should perform this modification from your GitHub account that is already linked to Ansys. Could you open the same PR from your other GH account?