Fix compiler warning.

./qmacpasteboardmime.h:57:10: warning: private field 'type' is not used [-Wunused-private-field]
    char type;
         ^

Change-Id: I69cfd93de446cd78d32c2d346b8cb1cb1b0acd93
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@digia.com>