Beckhoff/TC: velocity forwarding not working

[rerpha]

I missed a typo when converting to use the template/substitution files for the twincat fields, see difference between record names in here:
ISISComputingGroup/EPICS-ioc@44915ae
vs here: https://github.com/ISISComputingGroup/EPICS-motorExtensions/blob/master/beckhoffApp/Db/single_axis_tc.substitutions#L41-L42

This is really more of a flash review, but I wanted to add some release notes.

[rerpha]

typo fix: ISISComputingGroup/EPICS-motorExtensions#58
release notes: #8041

we don't really need to patch this anywhere as all velocities will have been set up at comissioning, but for any future beckhoffs this would be ideal to have.