run-tests: fix a typo in an attribute name
At least, I assume it's a typo. Nothing else uses it, but `_tmpbindir` is used.
Differential Revision: https://phab.mercurial-scm.org/D9542
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"phabricator.uri": "https://phab.mercurial-scm.org/",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}