Auto merge of #12185 - emilio:dont-reexpire-animations, r=nox

style: Do not re-expire animations.

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #12171 (github issue number if applicable).

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- [x] These changes do not have tests because they depend on weird timing conditions.

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If we're restyling a page with animations and layout takes too long, we
might still have the expired animations from the last restyle, without these
being cleared out by layout on `tick_animations`.

Unfortunately it's hard (near to impossible?) to make a reduced test case for
this, since it heavily depends on the speed of the build and conditions that
only happen under heavy loads.

Mainly, it depends on how accurately the `TickAllAnimations` message is sent
from the constellation.

Thus, we can't just re-expire an animation, and we should re-check for it as a
previous animation.

Fixes #12171

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