Revert "Update list.pyi"

This reverts commit eec3dfa.

Author: exertustfm

test-data/unit/fixtures/list.pyi

@@ -25,7 +25,6 @@ class list(Sequence[T]):
     def __setitem__(self, x: int, v: T) -> None: pass
     def append(self, x: T) -> None: pass
     def extend(self, x: Iterable[T]) -> None: pass
-    def copy(self) -> list[T]: pass
 
 class tuple(Generic[T]): pass
 class function: pass