[3.9] bpo-40924: Revert "bpo-39791 native hooks for importlib.resources.files (GH-20576)" (#20760)

This reverts commit 9cf1be46e3692d565461afd3afa326d124d743dd due to
https://bugs.python.org/issue40924.
diff --git a/Lib/importlib/abc.py b/Lib/importlib/abc.py
index 0b20e7c..b8a9bb1 100644
--- a/Lib/importlib/abc.py
+++ b/Lib/importlib/abc.py
@@ -468,7 +468,7 @@
         raise FileNotFoundError(resource)
 
     def is_resource(self, path):
-        return self.files().joinpath(path).is_file()
+        return self.files().joinpath(path).isfile()
 
     def contents(self):
         return (item.name for item in self.files().iterdir())