Temporarily revert PR #2885 (filename column in peers view).

There's a bug that causes frequent crashes.
Issue #4597.

src/base/bittorrent/peerinfo.h

@@ -100,7 +100,6 @@ namespace BitTorrent
 #ifndef DISABLE_COUNTRIES_RESOLUTION
         QString country() const;
 #endif
-        int downloadingPieceIndex() const;
 
     private:
         void calcRelevance(const TorrentHandle *torrent);