py3: restore perfstartup() prior to b456b2e0ad9f on Windows
Otherwise the test errors out with:
--- c:/Users/Matt/projects/hg_py3/tests/test-contrib-perf.t
+++ c:/Users/Matt/projects/hg_py3/tests/test-contrib-perf.t.err
@@ -184,6 +184,8 @@
$ hg perfrevrange
$ hg perfrevset 'all()'
$ hg perfstartup
+ 'b'c:' is not recognized as an internal or external command,
+ operable program or batch file.
$ hg perfstatus
$ hg perftags
$ hg perftemplating
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}