Update intro.mdx

remove the part that tells you to install @testing-library/dom because it is already included when using a framework wrapper

Author: skonky

docs/react-testing-library/intro.mdx

@@ -9,11 +9,10 @@ APIs for working with React components.
 
 ## Installation
 
-To get started with `React Testing Library`, you'll need to install it together
-with its peerDependency `@testing-library/dom`:
+To get started with `React Testing Library`, you'll need to install it.
 
 ```bash npm2yarn
-npm install --save-dev @testing-library/react @testing-library/dom
+npm install --save-dev @testing-library/react
 ```
 
 ### With TypeScript
@@ -22,7 +21,7 @@ To get full type coverage, you need to install the types for `react` and `react-
 well:
 
 ```bash npm2yarn
-npm install --save-dev @testing-library/react @testing-library/dom @types/react @types/react-dom
+npm install --save-dev @testing-library/react @types/react @types/react-dom
 ```
 
 [gh]: https://github.com/testing-library/react-testing-library