fix: accessing static variable using 'this' in instance method

Author: rchougule

src/main/java/com/browserstack/client/BrowserStackClient.java

@@ -176,7 +176,7 @@ public void setProxy(final String proxyHost, final int proxyPort, final String p
         }
 
         final HttpClient client = clientBuilder.build();
-        this.HTTP_TRANSPORT = new ApacheHttpTransport(client);
+        HTTP_TRANSPORT = new ApacheHttpTransport(client);
         this.requestFactory = newRequestFactory();
     }