Improved Spool Wheel (print without support) for RMU inspired MMU2S Buffer

I really appreciate Manzn's awesome work on the RMU inspired MMU2S Buffer. Unfortunately a clean print of their supplied spool wheels is not possible without using supports, which are tedious to remove and often leave remains nonetheless. These wheels are the most relevant pieces of the device in order to function with no trouble and you definitely don't want to risk an unnecessary uneven friction. That's why this remix fixes this minor flaw by replacing the wheel's inner “tub” with a chamfered arc, which is much easier to print, requires no supports at all and usually results in a pristine output. Print settings are the same as the original.