docs: update Next.js 15 versions in upgrade guide (#74960)

Author: leerob

docs/01-app/03-building-your-application/11-upgrading/03-version-15.mdx

@@ -13,10 +13,10 @@ To update to Next.js version 15, you can use the `upgrade` codemod:
 npx @next/codemod@canary upgrade latest
 ```
 
-If you prefer to do it manually, ensure that you're installing the latest Next & React RC, e.g.:
+If you prefer to do it manually, ensure that you're installing the latest Next & React versions:
 
 ```bash filename="Terminal"
-npm i next@latest react@rc react-dom@rc eslint-config-next@latest
+npm i next@latest react@latest react-dom@latest eslint-config-next@latest
 ```
 
 > **Good to know:**