Bug 1651910 - Fix a silly typo for the forward declaration Layer. r=botond

Differential Revision: https://phabricator.services.mozilla.com/D83038

gfx/layers/CompositorAnimationStorage.h

@@ -17,7 +17,7 @@
 namespace mozilla {
 namespace layers {
 class Animation;
-class Layers;
+class Layer;
 class CompositorBridgeParent;
 
 typedef nsTArray<layers::Animation> AnimationArray;