chore: update readme

Author: Ankit098

README.md

@@ -1,7 +1,7 @@
 # webdriverio-browserstack
 [WebdriverIO](http://webdriver.io/) Integration with BrowserStack.
 
-Master branch contains **Selenium 3** samples, for **Selenium 4 - W3C protocol** please checkout [selenium-4](https://github.com/browserstack/webdriverio-browserstack/tree/selenium-4) branch
+Master branch contains code samples using the **wdio-browserstack-service**, to run tests **without the service** please checkout [vanilla-integration](https://github.com/Ankit098/webdriverio-browserstack/tree/vanilla-integration) branch
 
 ![BrowserStack Logo](https://d98b8t1nnulk5.cloudfront.net/production/images/layout/logo-header.png?1469004780)