Prefer setq-local in most of textmodes/*.el

Prefer setq-local in most of textmodes/*.el

* lisp/textmodes/artist.el (artist-mode-init):
* lisp/textmodes/bibtex.el (bibtex-mode):
* lisp/textmodes/dns-mode.el (dns-mode):
* lisp/textmodes/enriched.el (enriched-mode):
* lisp/textmodes/ispell.el (ispell-buffer-local-parsing):
* lisp/textmodes/nroff-mode.el (nroff-mode):
* lisp/textmodes/picture.el (picture-mode):
* lisp/textmodes/refill.el (refill-mode):
* lisp/textmodes/two-column.el (2C-split): Prefer setq-local.