Fixes typo in autoloading_and_reloading_constants guide [ci skip]

The javascript directory under app/ is in a singular form (app/javascript) but the documentation was mentionning it in the plural form (app/javascripts).

Author: yoones

guides/source/autoloading_and_reloading_constants.md

@@ -90,7 +90,7 @@ INFO. Autoload paths are called _root directories_ in Zeitwerk documentation, bu
 
 Within an autoload path, file names must match the constants they define as documented [here](https://github.com/fxn/zeitwerk#file-structure).
 
-By default, the autoload paths of an application consist of all the subdirectories of `app` that exist when the application boots ---except for `assets`, `javascripts`, `views`,--- plus the autoload paths of engines it might depend on.
+By default, the autoload paths of an application consist of all the subdirectories of `app` that exist when the application boots ---except for `assets`, `javascript`, `views`,--- plus the autoload paths of engines it might depend on.
 
 For example, if `UsersHelper` is implemented in `app/helpers/users_helper.rb`, the module is autoloadable, you do not need (and should not write) a `require` call for it: