Improved X parallizer Anet E10 GT2 belt

I improved the X-Belt-Parallizer for the Anet E10 to better suit my needs:

- Belt is now 2mm higher to keep it from touching the wheel of the carriage
- The whole part is 2.5mm thicker to give it more stability; my previous parallizer broke after a while and it's a pain to change it...
- the slots are slightly wider because I struggled to get the belt in there