Remove checks for "stage_controller" in piezoscanner.py

[gadamc]

In the CounterAndScanner object defined in
https://github.com/qt3uw/qt3-utils/blob/main/src/qt3utils/datagenerators/piezoscanner.py
there are multiple lines where we check for the self.stage_controller (to essentially not be None).
However, this object cannot be instantiated without a stage_controller passed in. Thus, these checks are
pointless and should be removed.

https://github.com/qt3uw/qt3-utils/blob/main/src/qt3utils/datagenerators/piezoscanner.py#L42
https://github.com/qt3uw/qt3-utils/blob/main/src/qt3utils/datagenerators/piezoscanner.py#L60
https://github.com/qt3uw/qt3-utils/blob/main/src/qt3utils/datagenerators/piezoscanner.py#L95
https://github.com/qt3uw/qt3-utils/blob/main/src/qt3utils/datagenerators/piezoscanner.py#L122
https://github.com/qt3uw/qt3-utils/blob/main/src/qt3utils/datagenerators/piezoscanner.py#L164-L169