tests/test-diff-newlines.t

heptapod-ci: actually give pytest more time before timeout

`HGTEST_TIMEOUT` is overridden by `HGTEST_SLOWTIMEOUT` for tests marked as
slow, which `test-check-pytype.t` is. So this whole time the timeout was 1500s
(or 25 minutes), which is unfortunately not long enough for a *lot* of the
times it's run on the CI.

Differential Revision: https://phab.mercurial-scm.org/D11717

  $ hg init

  $ "$PYTHON" -c 'open("a", "wb").write(b"confuse str.splitlines\nembedded\rnewline\n")'
  $ hg ci -Ama -d '1 0'
  adding a

  $ echo clean diff >> a
  $ hg ci -mb -d '2 0'

  $ hg diff -r0 -r1
  diff -r 107ba6f817b5 -r 310ce7989cdc a
  --- a/a	Thu Jan 01 00:00:01 1970 +0000
  +++ b/a	Thu Jan 01 00:00:02 1970 +0000
  @@ -1,2 +1,3 @@
   confuse str.splitlines
   embedded\r (no-eol) (esc)
  newline
  +clean diff