api [nfc]: Use RawParameter when passing queue_id

Strings in general should not be JSON-encoded in Zulip APIs.

We will handle local_id separately because that's a bit different.

Author: PIG208

lib/api/route/messages.dart

@@ -193,7 +193,7 @@ Future<SendMessageResult> sendMessage(
         'to': destination.userIds,
       }}),
     'content': RawParameter(content),
-    if (queueId != null) 'queue_id': queueId, // TODO should this use RawParameter?
+    if (queueId != null) 'queue_id': RawParameter(queueId),
     if (localId != null) 'local_id': localId, // TODO should this use RawParameter?
     if (readBySender != null) 'read_by_sender': readBySender,
   },

test/api/route/messages_test.dart

@@ -362,7 +362,7 @@ void main() {
             'to': streamId.toString(),
             'topic': topic,
             'content': content,
-            'queue_id': '"abc:123"',
+            'queue_id': 'abc:123',
             'local_id': '"456"',
             'read_by_sender': 'true',
           });