c++: Fix deferred noexcept on constructor [PR93901].

c++: Fix deferred noexcept on constructor [PR93901].

My change in r10-4394 to only update clones when we actually instantiate a
deferred noexcept-spec broke this because deferred parsing updates the
primary function but not the clones.  For GCC 10, let's just revert it.

gcc/cp/ChangeLog
2020-03-10  Jason Merrill  <jason@redhat.com>

	PR c++/93901
	* pt.c (maybe_instantiate_noexcept): Always update clones.