Federal authorities want a judge to partially close his courtroom when a confidential FBI witness testifies this fall against the accused ISIS sympathizer prosecutors say threatened to behead the witness if he squealed to law enforcement.Alleged terrorist David Daoud Wright, 28, of Everett, told the witness in 2015 that if he learned a fellow Muslim betrayed him, Wright “would personally remove his head from his body,” according to documents filed with U.S.