The suspects texted one another as though they had everyone fooled. “How’s the rabbi?” one asked in a message. “Is he still scheduled for surgery?” “We are still waiting for the doctor to check if it’s still needed,” came the response. But there was no surgery, authorities say, and there was no rabbi. Instead, prosecutors allege, the men were referring to Amazon’s impending acquisition of the vacuum company iRobot, hoping to trade on what was th…