stage: Remove an extra reference count
stage: Remove an extra reference count

The dispose sequence will keep the object alive, and we need to release
the last reference held by the StageManager before releasing control to
GObject.

Distrotech/clutter,ebassi/clutter,jigpu/clutter,Distrotech/clutter,ebassi/clutter,djdeath/clutter-android,djdeath/clutter,heysion/clutter-clone,jigpu/clutter,ebassi/clutter,djdeath/clutter-android,djdeath/clutter,djdeath/clutter,GNOME/clutter,GNOME/clutter,heysion/clutter-clone,heysion/clutter-clone,collects/clutter,djdeath/clutter-android,djdeath/clutter,jigpu/clutter,collects/clutter,jigpu/clutter,Distrotech/clutter,collects/clutter,djdeath/clutter,djdeath/clutter,GNOME/clutter,collects/clutter,heysion/clutter-clone,djdeath/clutter-android,heysion/clutter-clone,ebassi/clutter,GNOME/clutter,jigpu/clutter,collects/clutter,GNOME/clutter,Distrotech/clutter,Distrotech/clutter,Distrotech/clutter,jigpu/clutter,djdeath/clutter-android,ebassi/clutter