Retention drops every child once they all age out, partman refuses to
drop the last one, and with infinite_time_partitions off it will not
premake forward from a child that far in the past. The set is left with
one stale partition and no current one, so metrics land right back in
the default.
Set infinite_time_partitions on telegraf parents, in both the repair
script and the retention subcommand, and stop blaming the launcher when
pg_cron is not loaded at all.