appveyor: Turn this off until the problems can be diagnosed.
appveyor: Turn this off until the problems can be diagnosed.

I don't use Windows, so I'm not sure why appveyor is failing to build
the precommit tests and use covlib. PR's gladly accepted if someone
knows what's going on. Otherwise, I'll fix it after tackling other
lower-numbered issues.

jesserayadkins/lily,FascinatedBox/lily,jesserayadkins/lily,FascinatedBox/lily,FascinatedBox/lily,FascinatedBox/lily,jesserayadkins/lily