message_failed: Hide focus rectangle while animating.

The focus rectangle would spin along with the arrows, which looked bad.

We do want to allow focus rectangles on this element for keyboard interaction,
so we just disable the focus rectangle during the animation.

Fixes #24110.

static/styles/zulip.css

@@ -1078,6 +1078,7 @@ td.pointer {
 
         .rotating {
             display: inline-block;
+            outline: none;
 
             animation: rotate 1s infinite linear;
         }