Remove old GCC version workarounds

The minimum GCC version is now GCC 10.

Source/Core/Common/EnumFormatter.h

@@ -42,12 +42,9 @@
  *   constexpr formatter() : EnumFormatter(names) {}
  * };
  */
-template <auto last_member, typename = decltype(last_member)>
+template <auto last_member>
 class EnumFormatter
 {
-  // The second template argument is needed to avoid compile errors from ambiguity with multiple
-  // enums with the same number of members in GCC prior to 8.  See https://godbolt.org/z/xcKaW1seW
-  // and https://godbolt.org/z/hz7Yqq1P5
   using T = decltype(last_member);
   static_assert(std::is_enum_v<T>);