Revert addition of third argument to format_type().

Revert addition of third argument to format_type().

Including collation in the behavior of that function promotes a world view
we do not want.  Moreover, it was producing the wrong behavior for pg_dump
anyway: what we want is to dump a COLLATE clause on attributes whose
attcollation is different from the underlying type, and likewise for
domains, and the function cannot do that for us.  Doing it the hard way
in pg_dump is a bit more tedious but produces more correct output.

In passing, fix initdb so that the initial entry in pg_collation is
properly pinned.  It was droppable before :-(