Propagate QDQ only when scale and zp are scalar (#7492)
fix crash when DeQuantizeLinear's output is graph output
propagate only when scale and zp are scalar.
fix bug for is_modified= is_modified || TryCancelOutDQQPair(graph, dq_node, q_node); in which TryCancelOutDQQPair wouldn't be invoked if is_modified is true
