testrunner: fix updating of .testtimes file
We attempt to write the 5 most recent test timings to a file called
.testtimes, but we read previous results from a file called
.testtimes- (including the hyphen), so we ended up no more than a
single time per test.
Differential Revision: https://phab.mercurial-scm.org/D1961
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}