Incorrect stl file names in manual

The manual is still using r1 stl filenames, see this image ![image](https://github.com/VoronDesign/Voron-Tap/assets/1043363/cce0882c-dd26-4381-aea7-be272f1e60e0)

* 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`)