The third third-highest ranking officer in the Rhode Island State Police has resigned because he had an inappropriate relationship with a potential candidate for the force. Colonel Steven O’Donnell said Friday that Lieutenant Colonel Wilfred Hill has agreed to step down, just days after he was placed on administrative leave. Among Hill’s duties was overseeing the State Police training academy. O’Donnell said at a press conference that Hill violated ‘‘numerous’’ State Police policies but said Hill was otherwise an excellent employee. O’Donnell said the woman did not want to press charges.