Fix Python version dependency and requirements.txt location
Fix Python version dependency and requirements.txt location

A lot of ARL uses syntax not compatible with Python 2.x (e.g., type
annotations) so no going back now

SKA-ScienceDataProcessor/algorithm-reference-library,SKA-ScienceDataProcessor/algorithm-reference-library,SKA-ScienceDataProcessor/algorithm-reference-library,SKA-ScienceDataProcessor/algorithm-reference-library,SKA-ScienceDataProcessor/algorithm-reference-library