test/h2: ignore AH02430 for the whole TestRfc9113 class

  test/h2: ignore AH02430 for the whole TestRfc9113 class

  test_h2_203_02 intentionally triggers AH02430 (illegal response header
  char). Over HTTP/2 the error is logged late during stream teardown and
  can produce several lines, so the per-case ignore_recent() raced them
  and they leaked into a later test's check_error_log(). Move the ignore
  to an autouse class fixture (as conftest.py does for AH10400/AH00045)
  and add HttpdErrorLog.remove_ignored_lognos() to restore on teardown.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1934891 13f79535-47bb-0310-9956-ffa450edef68