Use language parameter to format Code even when passing code_file

[GniLudio]

Overview: What does this pull request change?

Allows the usage of the language parameter in combination with the code_fileparameterwhen creating aCode` object.

from manim import *

class TestScene(Scene):
    def construct(self):
        self.add(
            Code(
                code_file="main.py",
                language="text", # was ignored before
            )
        )

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

Further Information and Comments

• Changes nothing for when the language parameter is omitted.
• Especially useful when pygments can't find a lexer.

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

[chopan050]

LGTM!