Fix FOR UPDATE SQL on SQL Anywhere

It looks like there was a misunderstanding on SQL Anywhere with the `FOR UPDATE` SQL as this is actually a statement used in prepared statements and does not work the ANSI way in ORM. So I removed it in favour of the table lock hint implementation which works out quite well and makes the `getForUpdateSQL()` rather useless anyways. SQL Server does it like this, too btw and both dialects are pretty similar because SQL Anywhere once derived from it.