Merge branch 'js/test-modernize-t9300'

Clean up style in an ancient test.

* js/test-modernize-t9300:
  modernize t9300: move test preparations into test_expect_success
  modernize t9300: mark here-doc words to ignore tab indentation
  modernize t9300: use test_when_finished for clean-up
  modernize t9300: wrap lines after &&
  modernize t9300: use test_must_be_empty
  modernize t9300: use test_must_fail
  modernize t9300: single-quote placement and indentation