[web-animations-1] Make animations with zero playback rate in before/after phase NOT be considered "current"

See w3c#3193

Author: birtles

web-animations-1/Overview.bs

@@ -2295,7 +2295,7 @@ of the following conditions are true:
 
 *   the [=animation effect=] is [=in play=], or
 *   the [=animation effect=] is [=associated with an animation=] with
-    a [=playback rate=] ≥ 0 and
+    a [=playback rate=] > 0 and
     the [=animation effect=] is in the [=before phase=], or
 *   the [=animation effect=] is [=associated with an animation=] with
     a [=playback rate=] < 0 and