Help text assumes Pathauto route exists without declaring Pathauto dependency

Problem/Motivation

The help hook always calls `Url::fromRoute('entity.pathauto_pattern.collection')` when rendering help for the route path alias collection, add, and edit pages. The module does not declare Pathauto as a dependency, so that route is absent on sites that install Route Path Alias without Pathauto. Rendering those admin pages can therefore fail with a route-not-found exception.

Symfony\Component\Routing\Exception\RouteNotFoundException: Route "entity.pathauto_pattern.collection" does not exist. in Drupal\Core\Routing\RouteProvider->getRouteByName() (line 214 of /var/www/html/xxxxx/web/core/lib/Drupal/Core/Routing/RouteProvider.php).

Steps to reproduce

1. Install Drupal 11 with Path Alias available, but do not install Pathauto.
2. Install Route Path Alias.
3. Visit `/admin/config/search/path/route-path-aliases` as a user with the
"Administer route path aliases" permission.
4. Let Drupal render the local help text for that route.

Expected
The route path alias admin page renders normally, with help text that only links to routes available on the site.

Actual
The help hook attempts to generate the missing `entity.pathauto_pattern.collection` route and can throw an exception before the page finishes rendering.

Proposed resolution

Either add Pathauto as a module dependency, or check whether the route exists before generating the Pathauto link and render plain text or omit that link when Pathauto is not installed.