Fix coverage check

[wulfraem]

Description of change

This PR updates the code instrument-coverage flag to be set as a stable option as this option has moved from unstable to stable.

It also adds a changelog entry for the previous (#223).

Type of change

Choose a type of change, and delete any options that are not relevant.

• Bug fix (a non-breaking change which fixes an issue)
• Enhancement (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Fix
• Chore

How the change has been tested

Code coverage command from CI ran successfully in local tests.

Change checklist

Add an x to the boxes that are relevant to your changes, and delete any items that are not.

• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes