2022-01-24 Update: Found out that this print is not needed anymore. In the latest firmware update you can change the Z-axis length. Go to Settings > press and hold HW Setup > Z Axis Length > increase 185 to 190. It may be a different value if you have a fystec clone of the bondtech extruder.
________________________________________________________________________________________________________________
The Prusa Mini z-axis self test will fail when using the Bondtech extruder because it is slightly shorter than the stock extruder. The z-axis will continue about 5mm pass the point where the software expects the resistance/collision. This spacer will sit on the Bondtech extruder and you can remove it whenever the test are done.
I got the idea from rickyh7 on the following reddit thread.
The author hasn't provided the model origin yet.