EPISCOPAL CHURCH leaders, acting to quell dissension in their ranks over plans to hold a convention next summer in Phoenix, say they will go ahead with the gathering - but spend less money while they're there. Church leaders will hold a "no-frills, basic convention and use some of our economic impact" to make the point that Arizona should adopt a holiday honoring Martin Luther King Jr., a church spokeswoman said . . . EGYPTIAN AUTHORITIES closed the tomb of Egyptian Pharaoh Tutankhamen after discovering fungus growing on priceless artifacts and said they do not expect to reopen it before next summer.