Remove dependance on index mots_notices
Actually search engine rely on two indexexes:
FULLTEXT KEY mots_notice (titres,auteurs,editeur,collection,matieres,dewey)
FULLTEXT KEY mots_notice_2 (titres,auteurs,editeur,collection,matieres,dewey,other_terms)
This commit ensure only the last one is used so the first one can be deleted later. This produce a 2x speedup on insert / delete / update requests