Fix the url

Author: olimpias

api/src/test/java/com/messagebird/ConversationMessagesTest.java

@@ -79,7 +79,7 @@ public void testSendMessage() throws GeneralException, UnauthorizedException {
         sendRequest.setReportUrl("https://example.com/reportUrl");
 
         MessageBirdService messageBirdService = SpyService
-                .expects("POST", "/send", sendRequest)
+                .expects("POST", "send", sendRequest)
                 .withConversationsAPIBaseURL()
                 .andReturns(new APIResponse(JSON_CONVERSATION_SEND_MESSAGE_RESPONSE));
         MessageBirdClient messageBirdClient = new MessageBirdClient(messageBirdService);