PruneTemporaryBindings results in an array index warning being issued twice

[secure-sw-dev-bot]

This issue was copied from checkedc/checkedc-clang#696

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After pruning temporary bindings from member expression bounds in #694, an "array index exceeds bounds" warning is issued twice in the following example (taken from the memory-access-checking test):

struct S { int i;  int j; };
struct S global_arr2 _Checked[10];
void f5(_Array_ptr<struct S> param_arr : count(10)) {
  _Ptr<int> p = &(global_arr2[11].i);
}