Tests: Revert removing empty directory in WP_UnitTestCase_Base::rmdir() for now.

This appears to need more investigation. Instead, delete the `test-plugin` and `link-manager` directories in REST API plugins controller tests, for which this change was initially intended.

Follow-up to [54300], [54301], [54303].

See #55652, #56629.

git-svn-id: https://develop.svn.wordpress.org/trunk@54304 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/tests/multisite/cleanDirsizeCache.php

@@ -295,6 +295,8 @@ if ( is_multisite() ) :
 
 			// Cleanup.
 			$this->remove_added_uploads();
+			rmdir( $upload_dir['basedir'] . '/2/1' );
+
 			restore_current_blog();
 		}