Fix assert in bounds widening "BinaryNode operator must equal parent operator"

[mgrang]

Handle the following case in bounds widening:

void f(int i) {
  _Nt_array_ptr<char> p : count(0) = "a";

  if (*(p + (0 * 1)))
  {}
}

Currently, we hit an assert:

clang-9: /usr/local/magrang/master/src/clang/lib/AST/PreorderAST.cpp:46: void clang::PreorderAST::RemoveNode(clang::Node*, clang::Node*): Assertion `B->Opc == P->Opc && "BinaryNode operator must equal parent operator"' failed.

This is because we have incorrectly added the requirement that in order to remove a BinaryNode its opcode should be equal to its parent opcode which is not valid in this case.

[mgrang]

Fixed in #943