Remove unnecessary messaging workaround

A better fix was introduced in e36c702 for this issue.

The actual problem was that Safari when sends a message from the
background to content, then it passes to all the frames in the target tab,
but it doesn't make copies, it passes only references to the same object,
so if one frame modifies the message, then other frames would have
received the modified message.

src/js/vapi-client.js

@@ -29,6 +29,8 @@ var messagingConnector = function(response) {
 
     if (response.requestId) {
         listener = vAPI.messaging.listeners[response.requestId];
+        delete vAPI.messaging.listeners[response.requestId];
+        delete response.requestId;
     }
 
     if (!listener) {
@@ -37,14 +39,6 @@ var messagingConnector = function(response) {
     }
 
     if (typeof listener === 'function') {
-        // Safari bug
-        // Deleting the response.requestId below (only in some cases, probably
-        // when frames are present on the page) will remove it from all the
-        // future messages too, however with the following line it won't.
-        vAPI.safari && console.log;
-
-        delete vAPI.messaging.listeners[response.requestId];
-        delete response.requestId;
         listener(response.msg);
     }
 };