Make sleep a full second so database has a chance to update.

test/unit/php/includes/core/classes/class-test-rsvp.php

@@ -138,7 +138,7 @@ public function test_check_waiting_list(): void {
 		$rsvp->save( $user_1_id, 'not_attending' );
 
 		// Give it a slight delay to move member from waiting_list to attending (w/o test sometimes fails).
-		sleep( .1 );
+		sleep( 1 );
 
 		$this->assertSame( 'attending', $rsvp->get( $user_3_id )['status'], 'Failed to asser user 3 is on attending.' );
 		$this->assertSame( 0, $rsvp->check_waiting_list(), 'Failed to assert expected waiting list value.' );