Change from "XFAIL: libcpp-no-exceptions" to "UNSUPPORTED:...

Change from "XFAIL: libcpp-no-exceptions" to "UNSUPPORTED: libcpp-no-exceptions" tests that only check exceptions and nothing else

This is a follow up of D24562.

These tests do not check anything but exceptions, so it makes sense to mark
them as UNSUPPORTED under a library built without exceptions.

Differential Revision: https://reviews.llvm.org/D26075

llvm-svn: 285550