text: Update get_paint_volume() implementation
text: Update get_paint_volume() implementation

In commit 9818eee4646e49e99beb5a43f1dafcbdcca41f94 I forgot to update
ClutterText as well as the other actors.

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