[#3521203] Enable GitlabCI.

Merge [#3290418] prior to this MR. Temporarily included in this MR to allow tests to run & pass.

tests/src/Functional/PageCacheTest.php

@@ -18,6 +18,11 @@ class PageCacheTest extends BrowserTestBase {
 
   protected static $modules = ['views', 'views_advanced_cache_test'];
 
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
   protected $strictConfigSchema = FALSE;
 
   /**
@@ -47,7 +52,6 @@ class PageCacheTest extends BrowserTestBase {
       'config:views.view.views_advanced_cache_test',
       'http_response',
       'rendered',
-      'user:0',
       'vact:node_list:test',
     ];