Revert "Diagnose UnresolvedLookupExprs that resolve to instance members in static...

Revert "Diagnose UnresolvedLookupExprs that resolve to instance members in static methods"

This reverts commit r250592.

It has issues around unevaluated contexts, like this:
  template <class T> struct A { T i; };
  template <class T>
  struct B : A<T> {
    using A<T>::i;
    typedef decltype(i) U;
  };
  template struct B<int>;

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@250774 91177308-0d34-0410-b5e6-96231b3b80d8