tests: disable test-nointerrupt on Windows

Per the followup discussion[1].  proc.send_signal(INT) in timeout.py raises a
ValueError because of an unsupported signal.  I don't like missing test coverage
for this on Windows.  But this is the last test failing on Windows, and red all
the time hides new failures.

[1] https://phab.mercurial-scm.org/D3716

tests/test-nointerrupt.t

@@ -1,83 +1,85 b''
+#require no-windows
+
 Dummy extension simulating unsafe long running command
   $ cat > sleepext.py <<EOF
   > import itertools
   > import time
   > 
   > from mercurial.i18n import _
   > from mercurial import registrar
   > 
   > cmdtable = {}
   > command = registrar.command(cmdtable)
   > 
   > @command(b'sleep', [], _(b'TIME'), norepo=True)
   > def sleep(ui, sleeptime=b"1", **opts):
   >     with ui.uninterruptable():
   >         for _i in itertools.repeat(None, int(sleeptime)):
   >             time.sleep(1)
   >         ui.warn(b"end of unsafe operation\n")
   >     ui.warn(b"%s second(s) passed\n" % sleeptime)
   > EOF
 
 Kludge to emulate timeout(1) which is not generally available.
   $ cat > timeout.py <<EOF
   > from __future__ import print_function
   > import argparse
   > import signal
   > import subprocess
   > import sys
   > import time
   > 
   > ap = argparse.ArgumentParser()
   > ap.add_argument('-s', nargs=1, default='SIGTERM')
   > ap.add_argument('duration', nargs=1, type=int)
   > ap.add_argument('argv', nargs='*')
   > opts = ap.parse_args()
   > try:
   >     sig = int(opts.s[0])
   > except ValueError:
   >     sname = opts.s[0]
   >     if not sname.startswith('SIG'):
   >         sname = 'SIG' + sname
   >     sig = getattr(signal, sname)
   > proc = subprocess.Popen(opts.argv)
   > time.sleep(opts.duration[0])
   > proc.poll()
   > if proc.returncode is None:
   >     proc.send_signal(sig)
   >     proc.wait()
   >     sys.exit(124)
   > EOF
 
 Set up repository
   $ hg init repo
   $ cd repo
   $ cat >> $HGRCPATH << EOF
   > [extensions]
   > sleepext = ../sleepext.py
   > EOF
 
 Test ctrl-c
   $ python $TESTTMP/timeout.py -s INT 1 hg sleep 2
   interrupted!
   [124]
 
   $ cat >> $HGRCPATH << EOF
   > [experimental]
   > nointerrupt = yes
   > EOF
 
   $ python $TESTTMP/timeout.py -s INT 1 hg sleep 2
   interrupted!
   [124]
 
   $ cat >> $HGRCPATH << EOF
   > [experimental]
   > nointerrupt-interactiveonly = False
   > EOF
 
   $ python $TESTTMP/timeout.py -s INT 1 hg sleep 2
   shutting down cleanly
   press ^C again to terminate immediately (dangerous)
   end of unsafe operation
   interrupted!
   [124]