specify a more correct Sprite.groups return type

Author: nachomaiz

buildconfig/stubs/pygame/sprite.pyi

@@ -106,7 +106,7 @@ class Sprite(_SupportsSprite):
     def remove(self, *groups: _Group) -> None: ...
     def kill(self) -> None: ...
     def alive(self) -> bool: ...
-    def groups(self) -> list[_Group]: ...
+    def groups(self) -> list[AbstractGroup[_SupportsSprite]]: ...
 
 # concrete dirty sprite implementation class
 class DirtySprite(Sprite, _SupportsDirtySprite):