fix: #3620483 Remove the empty metatag_display_extender from the two admin views

Issue: https://www.drupal.org/project/varbase_admin_base/issues/3620483

Both shipped admin views declared metatag_display_extender on their page_1 display with nothing in it:

display_extenders:
  metatag_display_extender:
    metatags: {  }
    tokenize: false

• config/views.view.content.yml → /admin/content
• config/views.view.user_admin_people.yml → /admin/people

Both are administrative listings behind access control, never indexed, with no SEO purpose. The stanza is export noise from a site that had metatag_views enabled at export time.

It is not harmless: the extender is provided by the metatag_views submodule of drupal/metatag, and this recipe does not require drupal/metatag at all. On a Varbase install the install profile enables the submodule and the gap is hidden. On a Drupal CMS base nothing does, and building either view fatals:

PluginNotFoundException: The "metatag_display_extender" plugin does not exist.
Valid plugin IDs for Drupal\views\Plugin\ViewsPluginManager are: default

This MR removes only the metatag_display_extender entry, leaving display_extenders: { } — the same shape the default display already had. No values are lost.

Relationship to the other fix: #3620423 installs metatag_views from varbase_seo_base and is already merged; it is not reverted. That keeps the submodule available for views that genuinely want metatags. This change removes the dependency from two admin listings that do not need it, so the recipe no longer relies on a module it does not require.

Verified on Drupal CMS 2.x / core 11.4.5 with drupal/educare:1.0.x-dev: the two configs are the only ones in this recipe carrying the extender, and both stanzas were empty.

AI-Generated: Yes

Checkpoints:

• File an issue
• Addition/Change/Update/Fix
• Testing to ensure no regression
• Automated unit testing coverage
• Automated functional testing coverage
• UX/UI designer responsibilities
• Readability
• Accessibility
• Performance
• Security
• Developer Documentation
• User Guide Documentation
• Reviewed by human
• Code review by maintainers
• Full testing and approval
• Credit contributors
• Review with the product owner
• Release notes snippet
• Release