Fix logging.getLevelName() type hints (python#2730)

`logging.getLevelName()` can take either an `int` and returns a `str` or
a `str` and returns an `int` when the level name (`str`) or level
(`int`) is one of the registered log levels. If the value passed in
isn't one of the registered log levels, it returns the string `"level
%s" % lvl` where `lvl` is the value passed in to the function.

stdlib/2and3/logging/__init__.pyi

@@ -348,7 +348,7 @@ fatal = critical
 
 def disable(lvl: int) -> None: ...
 def addLevelName(lvl: int, levelName: str) -> None: ...
-def getLevelName(lvl: int) -> str: ...
+def getLevelName(lvl: Union[int, str]) -> Any: ...
 
 def makeLogRecord(attrdict: Mapping[str, Any]) -> LogRecord: ...