HICTOP Prusa i3 Y-axis Belt Holder (rework)

Modified the HICTOP Prusa i3 Y-Axis belt holder to improve the following characteristics:
1. thicker jaws for holding belt, reducing the chance of belt becoming lose when printing for extended period of time and high temperature bed settings by increasing thickness (increasing tolerance)
2. increased the distance between the two jaws so belt from each side could be folded and be placed side by side inside the grove more easily so the belt lines up properly (the original design is too tigh