Change the wiki_pages tsvector_update_trigger to use
`pg_catalog.english` instead of `public.danbooru`. This changes how wiki
page text is parsed for full-text search to use the standard English
parser instead of test_parser. This is to prepare for dropping
test_parser. Using test_parser here was wrong anyway because it meant
that punctuation wasn't removed from words when indexing wiki pages for
full-text search.