calibre: switch to qt-5.5, fixes #12793

pkgs/top-level/all-packages.nix

···
 
   calcurse = callPackage ../applications/misc/calcurse { };
 
-  calibre = qt5.callPackage ../applications/misc/calibre {
+  calibre = qt55.callPackage ../applications/misc/calibre {
     inherit (pythonPackages) pyqt5 sip_4_16;
   };