[dynamic shapes] fix _maybe_evaluate_static axioms bug (#158672)

Summary: couldn't get a minimal repro, but xref for size change during dict iteration error: https://fb.workplace.com/groups/1075192433118967/posts/1709439696360901

Test Plan:
-

Rollback Plan:

Differential Revision: D78047846

Pull Request resolved: https://github.com/pytorch/pytorch/pull/158672
Approved by: https://github.com/bobrenjc93

torch/fx/experimental/symbolic_shapes.py

@@ -6263,7 +6263,7 @@ class ShapeEnv:
                 return
             self._resimplify_floor_div_axioms = False
             new_items = {}
-            for k, v in axioms.items():
+            for k, v in list(axioms.items()):
                 # A FloorDiv in implications could have became CleanDiv at this point, due to new facts
                 # to the shapeEnv. This handles such issue but its not ideal. This is the only expression
                 # simplification that depends on the global state of shape env.