tests: remove {a..h} bashism from remotenames
I'm not bothering with a check-code test because this is a weird
construct that I didn't even know existed before it was breaking the
BSD build, and it also appears to fail if /bin/sh is dash like it is
on our Linux builder.
Differential Revision: https://phab.mercurial-scm.org/D1605
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273ce12ad8f1` will report some style violations on a very old commit).