deps: Add missing Python dependencies

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Noticed during a test CI run:

ModuleNotFoundError: No module named 'trimesh'
ModuleNotFoundError: No module named 'pywavefront'

This is a problem with Manim itself (as very often it doesn't pin its dependencies correctly 🙄). See also 3b1b/manim#2439

We fix it here as a temporary workaround by manually installing the necessary dependencies.

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The GitHub Actions currently fail with this error:

AttributeError: 'NoneType' object has no attribute 'partition'

for this line in Manim. The reason is probably that this line is not working as intended, i.e. the clipboard-handling is problematic in the CI (although it worked completely fine one year ago)

code_string = pyperclip.paste()