Fix C++17 expected errors for pointer to member function template args.

* g++.dg/template/ptrmem20.C: Adjust expected diagnostic.
* g++.dg/template/ptrmem8.C: Likewise.

From-SVN: r264157

gcc/testsuite/g++.dg/template/ptrmem20.C

@@ -12,5 +12,5 @@ template<void (A::*)()> void bar(); // { dg-message "note" }
 
 void baz()
 {
-  bar<&B::foo>();  // { dg-error "template argument|no match" }
+  bar<&B::foo>();  // { dg-error "template argument|no match|convert" }
 }

gcc/testsuite/g++.dg/template/ptrmem8.C

@@ -15,8 +15,8 @@ template <int (D::*fun)() const> int Get(); // { dg-message "note" }
 
 int main () 
 {
-  Get<&B::I>();   // { dg-error "template argument|converted constant" "not valid" }
+  Get<&B::I>();   // { dg-error "template argument|convert" "not valid" }
   // { dg-error "no match" "no match" { target *-*-* } .-1 }
-  Get<&D::I>();   // { dg-error "template argument|converted constant" "not valid" }
+  Get<&D::I>();   // { dg-error "template argument|convert" "not valid" }
   // { dg-error "no match" "no match" { target *-*-* } .-1 }
 }