We can tell from its position in the sentence:

j’espère que plus personne n’a d’a priori.

that a priori is a noun phrase. It means a preconceived idea. It is synonym of un préjugé.

The phrase a (à) priori can also be:

• An adverbial phrase:

  Il ne faut écarter à priori aucune hypothèse.

• An adjective phrase:

  La modération à priori est une sécurité.

As an adverb or an adjective, it can be spelled a priori (old spelling, and then it is usually in italics as it is the Latin spelling) or « à priori » (1990 orthography reform). See Lequel d' « à priori » ou « a priori » est le plus correct ?)

When it is a noun phrase:

J’ai un a priori favorable pour la solution présentée.

It can be spelled a priori (no accent on the a) or as a single word: apriori (1990 orthography reform), and it is invariable.