clutter/actor: Remove superfluous line

This sets exactly the same thing as the line above and doesn't
manipulate any parts of the calculation, too, it's most likely a very
old copy-paste mistake, remove it.

Fixes GNOME/mutter#1222
13 jobs for fix-clutter-actor-copy-paste
Status Job ID Name Coverage
  Review
manual #1062838
manual
check-commit-log
manual #1062839
manual
check-merge-request
 
  Prepare
created #1062841
aarch64
build-fedora-container@aarch64
created #1062840
build-fedora-container@x86_64
 
  Build
created #1062843
aarch64
build-mutter@aarch64
created #1062842
build-mutter@x86_64
created #1062845
build-without-native-backend-and-wayland@x86_64
created #1062844
build-without-opengl-and-glx@x86_64
 
  Test
created #1062848
can-build-gnome-shell@x86_64
created #1062847
aarch64
test-mutter@aarch64
created #1062846
test-mutter@x86_64
 
  Coverage
created #1062850
aarch64
test-mutter-coverage@aarch64
created #1062849
test-mutter-coverage@x86_64