[web-animations-1] De-dup dfn of associated animation

Author: fantasai

web-animations-1/Overview.bs

@@ -2466,14 +2466,13 @@ Animation effects {#animation-effects}
   that provides a static description of some timed behavior.
 
 ### Relationship between animation effects and animations ### {#animation-effects-and-animations}
-
-  The [=associated effect=] of an [=animation=], if set,
-  is a type of [=animation effect=].
-  The [=associated effect=] of an [=animation=]
-  is said to be <dfn lt="associated with an animation">associated</dfn>
-  with that animation.
+  <p id="animation-effects-and-animations">
+  An [=animation effect=] is
+  <dfn for="animation effect" lt="associated animation"
+       local-lt="associated with an animation">associated with an animation</dfn>
+  when the effect is that animation’s [=associated effect=].
   At a given moment,
-  an [=animation effect=] can be [=associated with an animation|associated=]
+  an [=animation effect=] can be [=associated animation|associated=]
   with at most one [=animation=].
 
   An [=animation effect=], |effect|,
@@ -4248,11 +4247,6 @@ Combining effects {#combining-effects}
   of any two [=keyframe effects=] |A| and |B| within an [=effect stack=]
   is established by comparing their properties as follows:
 
-  1. Let the <dfn for="animation effect"
-      lt="associated animation">associated animation of an animation effect</dfn>
-      be the [=animation=] [=associated with an animation|associated=]
-      with the [=animation effect=].
-
   1. Sort |A| and |B|
       by applying the following conditions in turn
       until the order is resolved,