By Lisa Richwine LOS ANGELES (Reuters) -Johnny Depp’s attorney grilled the actor’s ex-wife Amber Heard on Tuesday, producing affectionate notes she wrote during their short-lived marriage to challenge her accounts of frequent violence and bolster the “Pirates of the Caribbean” star’s case for defamation. Depp, 58, is suing Heard for $50 million, saying she defamed him when she claimed she was a victim of domestic abuse. He has testified that he never hit Heard and argued that she was the abuser in their relationship. During her cross-examination, Depp lawyer Camille Vasquez showed jurors a kni…