Issue #3150070 by andypost: Fix new test modules variable visibility

core/modules/user/tests/src/Functional/UserLoginTest.php

@@ -19,11 +19,9 @@ class UserLoginTest extends BrowserTestBase {
   protected $defaultTheme = 'stark';
 
   /**
-   * Modules to install.
-   *
-   * @var array
+   * {@inheritdoc}
    */
-  public static $modules = ['dblog'];
+  protected static $modules = ['dblog'];
 
   /**
    * Tests login with destination.

core/modules/user/tests/src/Kernel/Controller/UserAuthenticationControllerTest.php

@@ -21,7 +21,7 @@ class UserAuthenticationControllerTest extends KernelTestBase {
   /**
    * {@inheritdoc}
    */
-  public static $modules = ['user'];
+  protected static $modules = ['user'];
 
   /**
    * @group legacy

core/modules/user/tests/src/Kernel/Form/UserLoginFormTest.php

@@ -18,7 +18,7 @@ class UserLoginFormTest extends KernelTestBase {
   /**
    * {@inheritdoc}
    */
-  public static $modules = ['user'];
+  protected static $modules = ['user'];
 
   /**
    * @group legacy