Change 'buildModules' to say 'modules'

As of Nuxt 3, `buildModules` property is deprecated. Use `modules` instead.

docs/content/1.getting-started/1.installation.md

@@ -21,7 +21,7 @@ Add `@nuxt/image-edge` as a devDependency to your project:
   ```
 ::
 
-Add the module to `buildModules` in your `nuxt.config`:
+Add the module to `modules` in your `nuxt.config`:
 
 ```ts [nuxt.config.js]
 export default {