Ignore a few override errors in typeshed (#19079)

I was seeing errors like these in our Bazel-based mypy configuration,
which may type check typeshed in some non-standard way:
```
mypy/typeshed/stdlib/tempfile.pyi:390: error: Argument 1 of "writelines" is incompatible with supertype "_IOBase"; supertype defines the argument type as "Iterable[Buffer]"  [override]
mypy/typeshed/stdlib/tempfile.pyi:390: note: This violates the Liskov substitution principle
mypy/typeshed/stdlib/tempfile.pyi:390: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#incompatible-overrides
mypy/typeshed/stdlib/tkinter/ttk.pyi:565: error: Signature of "forget" incompatible with supertype "Pack"  [override]
mypy/typeshed/stdlib/tkinter/ttk.pyi:565: note:      Superclass:
mypy/typeshed/stdlib/tkinter/ttk.pyi:565: note:          def pack_forget(self) -> None
mypy/typeshed/stdlib/tkinter/ttk.pyi:565: note:      Subclass:
mypy/typeshed/stdlib/tkinter/ttk.pyi:565: note:          def forget(self, tab_id: Any) -> None
```

I'm just merging this directly to the mypy repo so that I can move
forward more quickly, as this is needed to unblock the public release.

Author: JukkaL

mypy/typeshed/stdlib/tempfile.pyi

@@ -387,7 +387,7 @@ class SpooledTemporaryFile(IO[AnyStr], _SpooledTemporaryFileBase):
     def write(self: SpooledTemporaryFile[bytes], s: ReadableBuffer) -> int: ...
     @overload
     def write(self, s: AnyStr) -> int: ...
-    @overload
+    @overload  #  type: ignore[override]
     def writelines(self: SpooledTemporaryFile[str], iterable: Iterable[str]) -> None: ...
     @overload
     def writelines(self: SpooledTemporaryFile[bytes], iterable: Iterable[ReadableBuffer]) -> None: ...

mypy/typeshed/stdlib/tkinter/ttk.pyi

@@ -562,7 +562,7 @@ class Notebook(Widget):
         compound: tkinter._Compound = ...,
         underline: int = ...,
     ) -> None: ...
-    def forget(self, tab_id) -> None: ...
+    def forget(self, tab_id) -> None: ...  # type: ignore[override]
     def hide(self, tab_id) -> None: ...
     def identify(self, x: int, y: int) -> str: ...
     def index(self, tab_id): ...