tests: Update @since tags for backports

Follows-Up: I1054f6f944d491b536949cada33e2ac670e026f8
Follows-Up: If6a4c7dbba39389b06ce64fb5cac08cd8d7dd9fc
Change-Id: I6f4f060d5f47db19d9e705d3fe2f60395ab195dc

tests/phpunit/DynamicPropertyTestHelper.php

@@ -17,7 +17,7 @@ use Wikimedia\Assert\Assert;
  *
  * This class can be removed and its usages converted into direct WeakMap usage once MediaWiki only supports PHP 8.0 and above.
  *
- * @since 1.42
+ * @since 1.42 (also backported to 1.39.8, 1.40.4 and 1.41.2)
  * @internal Only for use by core PHPUnit setup functionality.
  */
 class DynamicPropertyTestHelper {

tests/phpunit/MediaWikiTestCaseTrait.php

@@ -123,7 +123,7 @@ trait MediaWikiTestCaseTrait {
 	/**
 	 * Skip the test if not running the necessary php version
 	 *
-	 * @since 1.42
+	 * @since 1.42 (also backported to 1.39.8, 1.40.4 and 1.41.2)
 	 *
 	 * @param string $op
 	 * @param string $version