Use implicit copy-constructor generated by compiler

This also suppresses the following clang warning:
warning: definition of implicit copy assignment operator for 'Version<unsigned short, 2>' is deprecated because it has a user-declared copy constructor [-Wdeprecated-copy]

src/base/bittorrent/infohash.h

@@ -64,7 +64,6 @@ namespace BitTorrent
 #endif
 
         InfoHash() = default;
-        InfoHash(const InfoHash &other) = default;
         InfoHash(const WrappedType &nativeHash);
 
         bool isValid() const;