refactor(tests): `getMockForTrait` is deprecated

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>

tests/lib/Memcache/CasTraitTest.php

@@ -18,7 +18,12 @@ class CasTraitTest extends TestCase {
 	 */
 	private function getCache() {
 		$sourceCache = new ArrayCache();
-		$mock = $this->getMockForTrait('\OC\Memcache\CasTrait');
+		$mock = $this->getMockBuilder(CasTraitTestClass::class)->onlyMethods([
+			'set',
+			'get',
+			'add',
+			'remove',
+		])->getMock();
 
 		$mock->expects($this->any())
 			->method('set')

tests/lib/Memcache/CasTraitTestClass.php

@@ -0,0 +1,24 @@
+<?php
+
+/**
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace Test\Memcache;
+
+use OC\Memcache\CASTrait;
+
+class CasTraitTestClass {
+	use CASTrait;
+
+	// abstract methods from Memcache
+	public function set($key, $value, $ttl = 0) {
+	}
+	public function get($key) {
+	}
+	public function add($key, $value, $ttl = 0) {
+	}
+	public function remove($key) {
+	}
+}