Fix ARIA label for the quote menu item (#618)

Resolves #604

src/directives/message_menu.html

@@ -18,7 +18,7 @@
         </md-menu-item>
         <md-menu-item ng-if="ctrl.access.quote">
             <md-button ng-click="ctrl.quote()">
-            <md-icon aria-label="Decline" class="material-icons md-24">format_quote</md-icon>
+            <md-icon aria-label="Quote" class="material-icons md-24">format_quote</md-icon>
             <span translate>messenger.QUOTE</span>
             </md-button>
         </md-menu-item>