fix(protocol-designer): ensure pipettes are removed from step forms when nuked (#2813)
fix(protocol-designer): ensure pipettes are removed from step forms when nuked (#2813)

We are changing the saved step forms when you edit your pipettes, the intended behavior included
updating the removed pipette references to null, although that action was not being dispatched if a
mount was set to null from a previously used mount.
OpenTrons/opentrons-api,Opentrons/labware,OpenTrons/opentrons-api,OpenTrons/opentrons-api,OpenTrons/opentrons_sdk,OpenTrons/opentrons-api,OpenTrons/opentrons-api