follow cover.sr.ht's rename to cov.sr.ht
The section in ecoretest's synthetic config.ini, and the grant vocabulary the
grants package uses for its examples — cover:upload was the stock example of a
well-formed grant, and the service that defines it now spells it cov:upload.
follow compare.sr.ht's rename to diff.sr.ht
The service renamed itself; what reaches this repository is the section name
in ecoretest's synthetic config.ini, which every service's switcher test is
built from, and the examples in the chrome docs and README that spelled the
old section. The fixture's custom services now read bench, cover, diff, dolt,
spec, tokens — alphabetical, which is the order BuildNav puts them in.