In my experience, parties in patent actions in the District of Delaware (and elsewhere) routinely drop claims in the lead up to trial. "Dropping claims" includes withdrawing asserted claims (e.g. "Claim 1"), whole asserted patents (e.g., "the '123 patent"), infringement contentions (e.g., "direct infringement" or "infringement by product A"), and other claims (including non-patent claims).
Most often, in practice, this is accomplished via an e-mail to the other side or, if the parties want something on the docket, by stipulation. I don't know of a case where the Court here insisted that a plaintiff not drop claims (of course, a defendant may also have counterclaims).
Are the Claims Withdrawn with Prejudice?
But parties rarely …