user proper id for mention

Signed-off-by: Andy Scherzinger <info@andy-scherzinger.de>

app/src/main/java/com/nextcloud/talk/ui/dialog/FilterConversationFragment.kt

@@ -134,7 +134,7 @@ class FilterConversationFragment(
             conversationsListActivity: ConversationsListActivity
         ) = FilterConversationFragment(savedFilterState, conversationsListActivity)
         val TAG: String = FilterConversationFragment::class.java.simpleName
-        const val MENTION: String = "TestmentionTest"
+        const val MENTION: String = "mention"
         const val UNREAD: String = "unread"
     }
 }