check for betterShadow support in the userAvatar instead of its parents

src/components/chat_message/chat_message.js

@@ -66,7 +66,6 @@ const ChatMessage = {
       return this.message.attachments.length > 0
     },
     ...mapState({
-      betterShadow: state => state.interface.browserSupport.cssFilter,
       currentUser: state => state.users.currentUser,
       restrictedNicknames: state => state.instance.restrictedNicknames
     }),

src/components/chat_message/chat_message.vue

@@ -20,7 +20,6 @@
         >
           <UserAvatar
             :compact="true"
-            :better-shadow="betterShadow"
             :user="author"
           />
         </UserPopover>