bpo-42053: Remove misleading check in os.fwalk() (pythonGH-27669)

os.fwalk() does not support integer as the first argument,
and never supported.

Lib/os.py

@@ -461,8 +461,7 @@ def fwalk(top=".", topdown=True, onerror=None, *, follow_symlinks=False, dir_fd=
                 dirs.remove('CVS')  # don't visit CVS directories
         """
         sys.audit("os.fwalk", top, topdown, onerror, follow_symlinks, dir_fd)
-        if not isinstance(top, int) or not hasattr(top, '__index__'):
-            top = fspath(top)
+        top = fspath(top)
         # Note: To guard against symlink races, we use the standard
         # lstat()/open()/fstat() trick.
         if not follow_symlinks: