docs: Mention the Timeline::stopped signal in the class description
docs: Mention the Timeline::stopped signal in the class description

Now that we have the ::stopped signal, it would be good if the
documentation mentioned it explicitly as the dual of the ::started
signal.

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