Setting restrictedtoken in pg_regress

In pg_regress we set restrictedToken when calling CreateRestrictedProcess, but
we never seem to use that anywhere.  Not being well versed in Windows I might
be missing something, but is it needed or is it a copy/pasteo from fa1e5afa8a2
which does that in restricted_token.c?  If not needed, removing it makes the
code more readable IMO.

--
Daniel Gustafsson        https://vmware.com/