Fix MathTex on experimental (#3871)

* Fix MathTex

example_scenes/test_new_rendering.py

@@ -3,6 +3,14 @@ from manim import *
 
 class Test(Scene):
     def construct(self) -> None:
+        self.play(
+            Create(
+                t := Tex(
+                    "Hello, world!", stroke_color=RED, fill_color=BLUE, stroke_width=2
+                )
+            )
+        )
+        self.play(FadeOut(t))
         s = Square()
         self.add(s)
         self.play(Rotate(s, PI / 2))

manim/mobject/text/tex_mobject.py

@@ -292,6 +292,11 @@ class MathTex(SingleStringMathTex):
             self._organize_submobjects_left_to_right()
         self.note_changed_family()
 
+        # 5 hours of work went into this line
+        # and it's still not perfect
+        # July 18, 2024
+        self.note_changed_family()
+
     def _break_up_tex_strings(self, tex_strings):
         # Separate out anything surrounded in double braces
         pre_split_length = len(tex_strings)