docs: Ignore clutter-test-utils.h
docs: Ignore clutter-test-utils.h

The API is public, because we need it in the conformance test suite, but
it's still a work in progress.

ebassi/clutter,djdeath/clutter,Distrotech/clutter,djdeath/clutter,Distrotech/clutter,ebassi/clutter,GNOME/clutter,Distrotech/clutter,Distrotech/clutter,djdeath/clutter,GNOME/clutter,GNOME/clutter,GNOME/clutter,jigpu/clutter,djdeath/clutter,Distrotech/clutter,jigpu/clutter,jigpu/clutter,ebassi/clutter,jigpu/clutter,Distrotech/clutter,ebassi/clutter,jigpu/clutter,GNOME/clutter,djdeath/clutter,ebassi/clutter,djdeath/clutter,jigpu/clutter