Use str.removeprefix and bump mypy python version

Author: JasonGrace2282

manim/mobject/mobject.py

@@ -679,13 +679,9 @@ def __getattr__(self, attr: str) -> types.MethodType:
         # Add automatic compatibility layer
         # between properties and get_* and set_*
         # methods.
-        #
-        # In python 3.9+ we could change this
-        # logic to use str.remove_prefix instead.
 
         if attr.startswith("get_"):
-            # Remove the "get_" prefix
-            to_get = attr[4:]
+            to_get = attr.removeprefix("get_")
 
             def getter(self):
                 warnings.warn(

mypy.ini

@@ -1,7 +1,7 @@
 [mypy]
 strict = False
 files = manim
-python_version = 3.10
+python_version = 3.11
 ; plugins = numpy.typing.mypy_plugin
 ignore_errors = False
 cache_fine_grained = True