Revert "clutter/offscreen-effect: Use the paint volume origin as the FBO offset"

This change broke the color picker in gnome-shell, let's revert it for
now until a correct solution can be figured out.

This reverts commit 0bace8db.

Closes GNOME/gnome-shell#3494
13 jobs for revert-offscreen-effect-fix
Status Job ID Name Coverage
  Review
manual #1043515
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check-commit-log
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check-merge-request
 
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build-fedora-container@aarch64
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build-mutter@aarch64
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build-mutter@x86_64
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build-without-native-backend-and-wayland@x86_64
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build-without-opengl-and-glx@x86_64
 
  Test
created #1043525
can-build-gnome-shell@x86_64
created #1043524
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test-mutter@aarch64
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test-mutter@x86_64
 
  Coverage
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test-mutter-coverage@aarch64
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test-mutter-coverage@x86_64