The C++ standard doesn't require that class template deduction guides
be templates themselves, but previously isDeductionGuide would assert
for the existence of a template closer or requires clause closer before
the deduction guide declaration.
This patch simply removes that check. Because of this, a test which
asserted that x()->x<1>; *isn't* a deduction guide failed, as it is
now formatted as a deduction guide. However, as @JohelEGP demonstrated,
it is [possible to make that a viable deduction guide].
Thus, that test has been removed, but other tests related to
non-template class template deduction guides have been added.