docs(readme): remove Yarn-specific installation instructions

Author: jrolfs

README.md

@@ -35,21 +35,12 @@ All of your favorite user-centric querying functions from **@testing-library/rea
 ### 1. Install
 
 ```bash
-# For use with Playwright
-npm install --save-dev playwright-testing-library
-
-# For use with Playwright Test
+# For use with Playwright Test (@playwright/test)
 npm install --save-dev @playwright-testing-library/test
-```
 
-or
-
-```bash
-# For use with Playwright
-yarn add --dev playwright-testing-library
+# For use with Playwright (playwright)
+npm install --save-dev playwright-testing-library
 
-# For use with Playwright Test
-yarn add --dev @playwright-testing-library/test
 ```
 
 ### 2a. Use _Playwright Test [fixture](https://playwright.dev/docs/test-fixtures)_