Resolve GlAvatar size in collapsed discussion replies

Updates the avatar size in collapsed replies to  24 to make it
compatible with GlAvatar when the gl_avatar_for_all_user_avatars
feature flag is enabled.

app/assets/javascripts/notes/components/toggle_replies_widget.vue

@@ -57,7 +57,7 @@ export default {
           :link-href="author.path"
           :img-alt="author.name"
           :img-src="author.avatar_url"
-          :img-size="26"
+          :img-size="24"
           :tooltip-text="author.name"
           tooltip-placement="bottom"
         />