Include Preview#url in service_urls_expire_in list [ci-skip]

Author: jonathanhefner

guides/source/configuring.md

@@ -2812,12 +2812,14 @@ Determines the default expiry of URLs generated by:
 
 * [`ActiveStorage::Blob#url`][]
 * [`ActiveStorage::Blob#service_url_for_direct_upload`][]
+* [`ActiveStorage::Preview#url`][]
 * [`ActiveStorage::Variant#url`][]
 
 The default is 5 minutes.
 
 [`ActiveStorage::Blob#url`]: https://api.rubyonrails.org/classes/ActiveStorage/Blob.html#method-i-url
 [`ActiveStorage::Blob#service_url_for_direct_upload`]: https://api.rubyonrails.org/classes/ActiveStorage/Blob.html#method-i-service_url_for_direct_upload
+[`ActiveStorage::Preview#url`]: https://api.rubyonrails.org/classes/ActiveStorage/Preview.html#method-i-url
 [`ActiveStorage::Variant#url`]: https://api.rubyonrails.org/classes/ActiveStorage/Variant.html#method-i-url
 
 #### `config.active_storage.urls_expire_in`