Mark dired-test-bug27243-02 as unstable for now

Mark dired-test-bug27243-02 as unstable for now

This appears to be a known issue:

  https://debbugs.gnu.org/cgi/bugreport.cgi?bug=27243#64
  https://debbugs.gnu.org/cgi/bugreport.cgi?bug=27243#115

Sample failure:

  Test dired-test-bug27243-02 backtrace:
    signal(ert-test-failed (((should (eq (point) pt1)) :form (eq 176 179
    ert-fail(((should (eq (point) pt1)) :form (eq 176 179) :value nil))
    #f(compiled-function () #<bytecode -0xdd3f9b8b64b2928>)()
    ert--run-test-internal(#s(ert--test-execution-info :test #s(ert-test
    ert-run-test(#s(ert-test :name dired-test-bug27243-02 :documentation
    ert-run-or-rerun-test(#s(ert--stats :selector (not ...) :tests [...
    ert-run-tests((not (or (tag :expensive-test) (tag :unstable))) #f(co
    ert-run-tests-batch((not (or (tag :expensive-test) (tag :unstable)))
    ert-run-tests-batch-and-exit((not (or (tag :expensive-test) (tag :un
    command-line-1(("-L" ":/<<PKGBUILDDIR>>/debian/
    command-line()
    normal-top-level()
  Test dired-test-bug27243-02 condition:
      (ert-test-failed
       ((should
         (eq
          (point)
          pt1))
        :form
        (eq 176 179)
        :value nil))
     FAILED   5/16  dired-test-bug27243-02 (0.010115 sec) at ../../build-src/test/lisp/dired-tests.el:189

Bug: https://debbugs.gnu.org/27243
Forwarded: not-needed