bug#40189: emacs-ts fails its test suite

[Maxim Cournoyer]

On master, emacs-ts fails one of its tests:

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   passed  28/35  ts-unix
Test ts-update backtrace:
  signal(ert-test-failed (((should (or (equal 31536000 (floor (ts-diff
  ert-fail(((should (or (equal 31536000 (floor (ts-difference ts one-y
  (if (unwind-protect (setq value-1854 (or (equal 31536000 (floor (ts-
  (let (form-description-1855) (if (unwind-protect (setq value-1854 (o
  (let ((value-1854 (gensym "ert-form-evaluation-aborted-"))) (let (fo
  (let* ((ts (ts-now)) (one-year-ago ts)) (setq one-year-ago (ts-fill 
  (closure (t) nil (let* ((ts (ts-now)) (one-year-ago ts)) (setq one-y
  ert--run-test-internal(#s(ert--test-execution-info :test #s(ert-test
  ert-run-test(#s(ert-test :name ts-update :documentation nil :body (c
  ert-run-or-rerun-test(#s(ert--stats :selector t :tests [#s(ert-test 
  ert-run-tests(t #f(compiled-function (event-type &rest event-args) #
  ert-run-tests-batch(nil)
  ert-run-tests-batch-and-exit()
  command-line-1(("-l" "test/test.el" "-f" "ert-run-tests-batch-and-ex
  command-line()
  normal-top-level()
Test ts-update condition:
    (ert-test-failed
     ((should
       (or
        (equal 31536000 ...)
        (equal 31622399 ...)))
      :form
      (or
       (equal 31536000
              (floor ...))
       (equal 31622399
              (floor ...)))
      :value nil))
   FAILED  29/35  ts-update
   passed  30/35  ts-year
   passed  31/35  ts<
   passed  32/35  ts<=
   passed  33/35  ts=
   passed  34/35  ts>
   passed  35/35  ts>=

Ran 35 tests, 34 results as expected, 1 unexpected (2020-03-23 01:14:41+0000)

1 unexpected results:
   FAILED  ts-update

command "emacs" "--batch" "-l" "test/test.el" "-f" 
"ert-run-tests-batch-and-exit" failed with status 1
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