Issue #3457486 by TR: Phpstan: Call to deprecated method getMockForAbstractClass()

Closes #3457486

tests/src/Unit/Integration/RulesAction/RulesAdminAccessTest.php

@@ -39,7 +39,7 @@ class RulesAdminAccessTest extends RulesIntegrationTestBase {
     $action = $this->getMockBuilder(RulesActionBase::class)
       ->disableOriginalConstructor()
       ->onlyMethods(['getPluginDefinition'])
-      ->getMockForAbstractClass();
+      ->getMock();
 
     $action
       ->expects($this->exactly(2))