user_dictionary_persists_through_a_file saves the whole user dictionary to
a file and loads it back. Run beside
user_dictionary_and_ignore_all_match_both_normalization_forms, it could
catch a word that test had added and bring it back after the test removed
it, so the other test's last check failed now and then (once in about two
dozen full runs here). It now holds DICTIONARY_TESTS, as the other test
does.