Use the correct term for NI-FGEN and NI-SCOPE devices

[sbethur]

Description of issue

NI-FGEN devices are referred to as Signal Generators. The correct term is Waveform Generators. Usages:

• https://github.com/ni/nimi-python/blob/02ebc9ed0bcc43f74d685b26f30a634c19a98e8c/src/nifgen/metadata/config.py#L58

NI-SCOPE devices are referred to as High Speed Digitizers. The correct term is Oscilloscopes. Usages:

• https://github.com/ni/nimi-python/blob/02ebc9ed0bcc43f74d685b26f30a634c19a98e8c/src/niscope/metadata/config.py#L55
• https://nimi-python.readthedocs.io/en/master/niscope.html?highlight=digitizer#usage
• https://nimi-python.readthedocs.io/en/master/nimodinst.html#usage