REST API: Exclude custom site health capability check on multisite.

Super admins will always pass capability checks.

Follow up to [49154], [49155].
See #48105.


git-svn-id: https://develop.svn.wordpress.org/trunk@49156 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/tests/rest-api/rest-site-health-controller.php

@@ -77,6 +77,9 @@ class WP_Test_REST_Site_Health_Controller extends WP_Test_REST_TestCase {
 		$this->assertErrorResponse( 'rest_forbidden', $response, 403 );
 	}
 
+	/**
+	 * @group ms-excluded
+	 */
 	public function test_custom_capability() {
 		wp_set_current_user( self::$admin );