ePaper2in13V4.py fails if instantiated with full=False

[peterhinch]

This line https://github.com/waveshareteam/Pico_ePaper_Code/blob/c9bcd84db5adf5f085353649a8a5c31492bc5fb8/pythonNanoGui/drivers/ePaper2in13V4.py#L50C18-L50C30 calls a non-existent method .init_partial.