[CodeHealth] Remove unnecessary function call in Animation ctor

AttachCompositorTimeline requires a compositor_animation_ which can only
be created during Animation::PreCommit().

Bug: None
Change-Id: I8fea8c9f787ad07fe77e3aaebedaa3bcbf9c5098
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2019470Reviewed-by: Stephen McGruer <smcgruer@chromium.org>
Commit-Queue: Yi Gu <yigu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735389}

third_party/blink/renderer/core/animation/animation.cc

@@ -216,7 +216,6 @@ Animation::Animation(ExecutionContext* execution_context,
   else
     document_->Timeline().AnimationAttached(this);
 
-  AttachCompositorTimeline();
   probe::DidCreateAnimation(document_, sequence_number_);
 }