Fix rendering of muscles in MuscleWidget

[thisisyoussef]

Ensure that when a muscle is both main and secondary, only the main muscle background is drawn. This addresses potential overlaps and redundant rendering in the MuscleWidget.

Proposed Changes

-Updated the build method in MuscleWidget to filter out secondary muscles that are also present in the main muscles list before rendering. -By doing so, we prevent the same muscle from being rendered twice, ensuring that only the main muscle background is displayed. -This approach retains the structure and readability of the code while addressing the issue.

Please check that the PR fulfills these requirements

• [X] Set a 100 character limit in your editor/IDE to avoid white space diffs in the PR
• [X] Tests for the changes have been added (for bug fixes / features)
• [X] Added yourself to AUTHORS.md