cookbook: Make filename used in video example consistent
cookbook: Make filename used in video example consistent

Fixed video filename in sample markup to match the
guidelines given in the "Contributing" section.

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