imghdr: h can be None (#3815)

stdlib/2and3/imghdr.pyi

@@ -10,7 +10,7 @@ else:
 
 
 @overload
-def what(file: _File) -> Optional[str]: ...
+def what(file: _File, h: None = ...) -> Optional[str]: ...
 @overload
 def what(file: Any, h: bytes) -> Optional[str]: ...
 tests: List[Callable[[bytes, BinaryIO], Optional[str]]]

tests/stubtest_whitelists/py3_common.txt

@@ -328,7 +328,6 @@ http.cookies.Morsel.update
 http.server.HTTPServer.__init__
 imaplib.IMAP4_SSL.ssl
 imaplib.IMAP4_stream.open
-imghdr.what
 importlib.abc.FileLoader.get_filename
 importlib.abc.Loader.exec_module
 importlib.abc.MetaPathFinder.find_spec