New upstream version for pg-ldap-sync

Hi All,

There is a new upstream version of pg-ldap-sync available (0.5.0 ->
0.5.1) and I have updated the packaging on s.d.o. It looks like the
build is failing for bullseye and focal. I am not an expert on Ruby but
it looks like the root cause is that these platforms provide ruby 2.7
while the other distributions provide ruby 3+. I think it might be
possible to provide a package tweak to enable this version to build on
bullseye and focal but given that both of these are rather old
distributions at this point, it might be exclude them from the build on
PGDG.

If there is no objection, I can push a commit to the apt.postgresql.org
repo excluding these distributions.

-- Bradford