Avoid useless copy. We only ever modify the current index, not anythi…

…ng we still need for the iteration.

Cython/Compiler/ExprNodes.py

@@ -5000,7 +5000,7 @@ def analyse_types(self, env, getting=True):
             return self
 
         axis_idx = 0
-        for i, index in enumerate(indices[:]):
+        for i, index in enumerate(indices):
             index = index.analyse_types(env)
             if index.is_none:
                 self.is_memview_slice = True