[css-animations-2] Keep final keyframe at the end.

Otherwise it won't be last if some other non-<percentage> keyframes
have an equivalent used offset.

Author: fantasai

css-animations-2/Overview.bs

@@ -361,16 +361,12 @@ its associated [=keyframes=] are generated as follows:
 
     *   The <dfn lt="computed keyframe order">computed order</dfn> of |keyframes|--
         which is the order returned by {{KeyframeEffect/getKeyframes()}}--
-        is found by
-        shifting |initial keyframe|, |final keyframe|, and
-        any keyframes whose offset was specified
-        as <<percentage>>, ''@keyframes/from'', or ''@keyframes/to''
-        to the front of the list,
+        is found by shifting any keyframes whose offset was specified as
+        a <<percentage>>, ''@keyframes/from'' keyword, or ''@keyframes/to'' keyword
+        to the front of the list (after the generated |initial keyframe|, if any),
         and performing a stable sort on these keyframes
         by their |keyframe offset|s.
 
-        ISSUE: It might be more natural to leave |final keyframe| at the end.
-
     *   The <dfn lt="used keyframe order">used order</dfn> of |keyframes|--
         which is the order used to interpolate and compute the actual animation frames--
         is found by attaching the |keyframes|
@@ -383,7 +379,8 @@ its associated [=keyframes=] are generated as follows:
     sorts keyframes with <<percentage>> offsets,
     it maintains keyframes specified with a <<timeline-range-name>>
     in their [=specified keyframe order=]--
-    after any <<percentage>> keyframes,
+    after any <<percentage>> keyframes
+    (other than a generated |final keyframe|),
     even if these come later in the [=used keyframe order=].
 
 <h2 id="animation-definition">