Typo in matRad_addMUdataFromMachine: Use of dij.mxaMU instead of dij.maxMU

[Yu-Sim]

Describe the bug
There is a typo in the function matRad_addMUdataFromMachine(machine, stf, dij) in the file matRad/util/matRad_addMUdataFromMachine.m. Specifically, in the section where information is added to the dij struct, the field dij.mxaMU appears to be a typo and should be dij.maxMU to be consistent with both the naming convention and with prior code (where dij.maxMU is initialized).

[wahln]

Thanks for catching this. You want to open a PR with the fix yourself or should we fix it?

[Yu-Sim]

You can fix this, thank you.