Update fixtures.py

Revert due to pytest-dev#6962.

src/_pytest/fixtures.py

@@ -1053,10 +1053,8 @@ def execute(self, request: SubRequest) -> _FixtureValue:
 
         my_cache_key = self.cache_key(request)
         if self.cached_result is not None:
-            # note: comparison with `==` can fail (or be expensive) for e.g.
-            # numpy arrays (#6497).
             cache_key = self.cached_result[1]
-            if my_cache_key is cache_key:
+            if my_cache_key == cache_key:
                 if self.cached_result[2] is not None:
                     _, val, tb = self.cached_result[2]
                     raise val.with_traceback(tb)