tests: Fix g_content_type_is_mime_type() test on OSX
tests: Fix g_content_type_is_mime_type() test on OSX

It should be passed a mime type not a content type.

https://bugzilla.gnome.org/show_bug.cgi?id=734946

endlessm/glib,endlessm/glib,endlessm/glib,johne53/MB3Glib,johne53/MB3Glib,johne53/MB3Glib,endlessm/glib,johne53/MB3Glib,johne53/MB3Glib,johne53/MB3Glib,endlessm/glib