GENEVA — The boss of Al Jazeera English warned staffers to avoid looking like they’re participating in political protests — just hours after one of the network’s reporters appeared to join a march calling for Israel to be kicked out of the Eurovision Song Contest, The Post has learned. Journalists at the Qatar-backed news outlet — long accused of being  a “Hamas mouthpiece”  by Israeli leaders — received the memo last month after reporter Charlie Angela broadcast a segment from a 2,000-strong