message: remove unneeded gcc workaround to make appveyor happy
diff: @@ -178,15 +178,7 @@ namespace ranges
  using compressed_pair<BaseSent, Adapt>::first;
  using compressed_pair<BaseSent, Adapt>::second;
  public:
  - #if __GNUC__
  - adaptor_sentinel() = default;
  - constexpr adaptor_sentinel(BaseSent sent, Adapt adapt)
  - : compressed_pair<BaseSent, Adapt>{
  - static_cast<BaseSent &&>(sent), static_cast<Adapt &&>(adapt)}
  - {}
  - #else
  using compressed_pair<BaseSent, Adapt>::compressed_pair;
  - #endif
  // All sentinels into adapted ranges have a base() member for fetching
  // the underlying sentinel.
  