Incorrect stl file names in manual

[wathiede]

The manual is still using r1 stl filenames, see this image

• All of them have the wrong suffix (r1 vs r8)
• Tap_Magent_(Left|Right)_r1.stl are now called Tap_Center_(left|right)_r8.stl
• [a]Tap_Center_r1.stl is now [a]_Tap_Center_r8.stl (extra _ before Tap)