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.

Thanks to Rafał Mikrut for discovering it.

Fixes GNOME/mutter#1222

Part-of: <GNOME/mutter!1660>
13 jobs for fix-clutter-actor-copy-paste
Status Job ID Name Coverage
  Review
manual #1065345
manual
check-commit-log
manual #1065346
manual
check-merge-request
 
  Prepare
created #1065348
aarch64
build-fedora-container@aarch64
created #1065347
build-fedora-container@x86_64
 
  Build
created #1065350
aarch64
build-mutter@aarch64
created #1065349
build-mutter@x86_64
created #1065352
build-without-native-backend-and-wayland@x86_64
created #1065351
build-without-opengl-and-glx@x86_64
 
  Test
created #1065355
can-build-gnome-shell@x86_64
created #1065354
aarch64
test-mutter@aarch64
created #1065353
test-mutter@x86_64
 
  Coverage
created #1065357
aarch64
test-mutter-coverage@aarch64
created #1065356
test-mutter-coverage@x86_64