refactor(tests): use OS constant over function

Use PHP's newer PHP_OS_FAMILY constant.

- Allows us to drop a legacy OC_Util method.
- This test isn't even enabled at the moment.

Signed-off-by: Josh <josh.t.richards@gmail.com>

tests/lib/Files/ViewTest.php

@@ -809,7 +809,7 @@ class ViewTest extends \Test\TestCase {
 		 */
 		$folderName = 'abcdefghijklmnopqrstuvwxyz012345678901234567890123456789';
 		$tmpdirLength = strlen(Server::get(ITempManager::class)->getTemporaryFolder());
-		if (\OC_Util::runningOnMac()) {
+		if (PHP_OS_FAMILY === 'Darwin') { // macOS
 			$depth = ((1024 - $tmpdirLength) / 57);
 		} else {
 			$depth = ((4000 - $tmpdirLength) / 57);