fix: infinite recursion caused by accessing color of a highlighted Ta…

[BHearron]

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

This PR fixes issue #4419.
Removes an unused type hint that mypy was flagging.

Links to added or changed documentation pages

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

[henrikmidtiby]

Please add a test that checks whether the infinite recursion occurs as described in issue #4419.
The test file could look like this.

from __future__ import annotations

from manim.mobject.table import Table
from manim.utils.color import GREEN

def test_highlight_cell_in_table():
    # Case taken from issue 4419, which triggers an infinite loop
    table = Table(
        [["This", "is a"],["simple", "table"]]
    )
    rect = table.get_highlighted_cell((1,1), color=GREEN)
    print(rect.color)

In addition to adding the test I would also like to have a second opinion from one of the other maintainers, as the color handling code in manim is quite complex...