Fixed inconsistent stroke width scaling for text in compound objects

[vihdutta]

Overview: What does this pull request change?

The current code for scale() in vectorized_mobject.py takes the root mobject's stroke width and sets stroke with family=True as the default. This results in that width being pushed to all descendants including objects with a zero stroke width which should keep their width #4648 . I've modified the code to scale each object's own stroke width which resolves the issue.

Motivation and Explanation: Why and how do your changes improve the library?

Links to added or changed documentation pages

I didn't modify any documentation other than the docstring text for vectorized_mobject.py under VMobject's scale() function for the scale_stroke description.

Further Information and Comments

This is my first time contributing to open source! Let me know if there's other things I had forgotten to consider (comments, documentation wise, etc.)

Reviewer Checklist

• The PR title is descriptive enough for the changelog, and the PR is labeled correctly
• If applicable: newly added non-private functions and classes have a docstring including a short summary and a PARAMETERS section
• If applicable: newly added functions and classes are tested

[behackl]

This does look reasonable to me, thanks for catching and fixing this!

[vihdutta]

Looks like everything's great! I'm new to open source so forgive the question, but how do I have this merged with the main branch now?