Fix default config to use correct pixel_height and pixel_width

[StevenH34]

Overview: What does this pull request change?

Fixes #4174

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

When creating a manim project via manim init project my-project --default the created manim.cfg file has the pixel_height and pixel_width swapped. This causes the example animations to be rendered incorrectly. I swapped the pixel_height and pixel_width back to the correct resolution.

Links to added or changed documentation pages

Further Information and Comments

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