doc htm_untag: column is not required
doc htm_untag: column is not required

html_untag() accepts HTML as string not column. We can not only pass
column value but also string literal.

cosmo0920/groonga,groonga/groonga,groonga/groonga,groonga/groonga,kenhys/groonga,komainu8/groonga,komainu8/groonga,komainu8/groonga,cosmo0920/groonga,redfigure/groonga,hiroyuki-sato/groonga,kenhys/groonga,hiroyuki-sato/groonga,cosmo0920/groonga,kenhys/groonga,myokoym/groonga,myokoym/groonga,redfigure/groonga,hiroyuki-sato/groonga,cosmo0920/groonga,kenhys/groonga,redfigure/groonga,redfigure/groonga,komainu8/groonga,hiroyuki-sato/groonga,komainu8/groonga,groonga/groonga,naoa/groonga,komainu8/groonga,kenhys/groonga,myokoym/groonga,myokoym/groonga,naoa/groonga,myokoym/groonga,redfigure/groonga,myokoym/groonga,komainu8/groonga,cosmo0920/groonga,myokoym/groonga,kenhys/groonga,naoa/groonga,kenhys/groonga,hiroyuki-sato/groonga,naoa/groonga,kenhys/groonga,hiroyuki-sato/groonga,groonga/groonga,komainu8/groonga,naoa/groonga,groonga/groonga,cosmo0920/groonga,cosmo0920/groonga,hiroyuki-sato/groonga,groonga/groonga,groonga/groonga,redfigure/groonga,naoa/groonga,redfigure/groonga,hiroyuki-sato/groonga,naoa/groonga,cosmo0920/groonga,naoa/groonga,redfigure/groonga,myokoym/groonga