run-tests: disable caching of the wheels when installing test Mercurial...
run-tests: disable caching of the wheels when installing test Mercurial
It seems like this command doesn't currently cause the wheels to be cached, but
since I already had to prevent `pip` from caching when building wheels in
1a09563a615c, and also disable it in a test in 30b5dc517ec2, let's just be
explicit that we don't want caching, in case the default behavior changes.