gom: Add "constructor" annotations for gom_filter_new_and/or
gom: Add "constructor" annotations for gom_filter_new_and/or

The first argument to these functions is a GomFilter*, meaning they
are incorrectly introspected as instance methods rather than constructors.

Add the (constructor) annotation to fix this.

https://bugzilla.gnome.org/show_bug.cgi?id=728517

chergert/gom,GNOME/gom,chergert/gom,chergert/gom,GNOME/gom