Increase priority value of "High"

It was observed that setting the priority of a file to High has almost
no effect, so increase its value.

src/gui/torrentcontentmodelitem.h

@@ -37,7 +37,7 @@
 #include <libtorrent/torrent_info.hpp>
 
 namespace prio {
-enum FilePriority {IGNORED=0, NORMAL=1, HIGH=2, MAXIMUM=7, MIXED=-1};
+enum FilePriority {IGNORED=0, NORMAL=1, HIGH=6, MAXIMUM=7, MIXED=-1};
 }
 
 class TorrentContentModelFolder;