Remove next tag from docs (#8323)

Remove `next` tag from docs

addons/docs/README.md

@@ -94,7 +94,7 @@ features as well. This chart captures the current state of support
 First add the package. Make sure that the versions for your `@storybook/*` packages match:
 
 ```sh
-yarn add -D @storybook/addon-docs@next
+yarn add -D @storybook/addon-docs
 ```
 
 Docs has peer dependencies on `react` and `babel-loader`. If you want to write stories in MDX, you may need to add these dependencies as well: