DOC: Improve word choice in install guide, given EPD vs Canopy

The installation guide previously claimed that EPD was now called Canopy,
but that is not so.  Canopy is distinct from EPD, and EPD appears to be
in end-of-life (I am speculating based on the Enthought website at time
of writing).
Also, cf. https://www.enthought.com/products/canopy/faq/
DOC TRIV: Strip by-line from README