Fixed wrong indentation in :class:.Code

[nyabkun]

Fixed Code mobject wrong indentation at the first line.

Overview: What does this pull request change?

Before:

After:

Edit: made it into an executable test code

from manim import *


class CodeIndentationTest(Scene):
    def construct(self):
        co = Code(
            code="""\
            def test():
                print("Hello")""",
            language="Python",
            insert_line_no=False,
        )

        self.add(co)
        self.wait()


with tempconfig(
    {
        "quality": "medium_quality",
        "preview": True,
        "save_last_frame": True,
        "write_to_movie": False,
    }
):
    scene = CodeIndentationTest()
    scene.render()

This is caused by pygments' bug. And It seems that they don't have the motivation to change this. pygments/pygments#961

Further Information and Comments

I also added the test code test_code_mobject.py.

I'm new here, so please point out any problems 😍😍😍

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

[k4pran]

LGTM thanks for this!

[behackl]

Thank you for your contribution! :-)

[nyabkun]

@behackl san, @ryanmccauley211 san.

Thank you very much for the review and approval ! 😄