mesonlib: remove filename parameter to mlog.warning

After tracing all the way down to the bottom of this (or really, adding
annotations so mypy can) it turns out that passing file would just be
ignored at the end of the mlog call stack, so it should be removed

mesonbuild/utils/universal.py

@@ -249,7 +249,7 @@ def check_direntry_issues(direntry_array: T.Union[T.Iterable[T.Union[str, bytes]
                 You are using {e!r} which is not a Unicode-compatible
                 locale but you are trying to access a file system entry called {de!r} which is
                 not pure ASCII. This may cause problems.
-                '''), file=sys.stderr)
+                '''))
 
 class SecondLevelHolder(HoldableObject, metaclass=abc.ABCMeta):
     ''' A second level object holder. The primary purpose