PHILADELPHIA — The national “Abandon Biden” movement on Monday launched an effort to encourage Muslim voters and allies in Pennsylvania to ditch President Joe Biden in November. Leaders of the movement, which seeks to punish Biden for supporting Israel and failing to call for a cease-fire in Gaza last year, gathered Monday at Independence Mall in Philadelphia. “You have not only abandoned the American people, you have abandoned humanity,” activist Hayla Solomon, 23, said at the rally. “Today and moving forward, we are holding you accountable for your negligence, heedlessness, and callousness. …