[docs] Document the destructor for Timeline
[docs] Document the destructor for Timeline

The rest of the API reference lists the destructor for the class
inside the constructor's return value -- except Timeline.

djdeath/clutter,ebassi/clutter,jigpu/clutter,GNOME/clutter,ebassi/clutter,djdeath/clutter,kerrickstaley/clutter-vala,dlespiau/clutter,GNOME/clutter,Distrotech/clutter,rkudiyarov/clutter_osx,djdeath/clutter,djdeath/clutter,tardyp/clutter,djdeath/clutter-multithreaded,ebassi/clutter,Distrotech/clutter,spatulasnout/clutter,dlespiau/clutter,spatulasnout/clutter,kerrickstaley/clutter-vala,jigpu/clutter,djdeath/clutter-android,djdeath/clutter-multithreaded,djdeath/clutter-android,collects/clutter,djdeath/clutter-android,collects/clutter,jigpu/clutter,Distrotech/clutter,jigpu/clutter,nobled/clutter,Distrotech/clutter,heysion/clutter-clone,spatulasnout/clutter,collects/clutter,tardyp/clutter,GNOME/clutter,rkudiyarov/clutter_osx,spatulasnout/clutter,djdeath/clutter-android,jigpu/clutter,djdeath/clutter-multithreaded,rkudiyarov/clutter_osx,djdeath/clutter-android,heysion/clutter-clone,tardyp/clutter,djdeath/clutter,jigpu/clutter,djdeath/clutter,djdeath/clutter-multithreaded,nobled/clutter,heysion/clutter-clone,heysion/clutter-clone,heysion/clutter-clone,kerrickstaley/clutter-vala,collects/clutter,collects/clutter,GNOME/clutter,rkudiyarov/clutter_osx,spatulasnout/clutter,ebassi/clutter,GNOME/clutter,ebassi/clutter,Distrotech/clutter,dlespiau/clutter,kerrickstaley/clutter-vala,nobled/clutter,Distrotech/clutter