Remove obsolete prohibition on function name matching a column name.

Remove obsolete prohibition on function name matching a column name.

ProcedureCreate formerly threw an error if the function to be created
has one argument of composite type and the function name matches some
column of the composite type.  This was a (very non-bulletproof) defense
against creating situations where f(x) and x.f are ambiguous.  But we
don't really need such a defense in the wake of commit b97a3465d, which
allows us to deal with such situations fairly cleanly.  This behavior
also created a dump-and-reload hazard, since a function might be
rejected if a conflicting column name had been added to the input
composite type later.  Hence, let's just drop the check.

Discussion: https://postgr.es/m/CAOW5sYa3Wp7KozCuzjOdw6PiOYPi6D=VvRybtH2S=2C0SVmRmA@mail.gmail.com