It wasn't previously mentioned that the index is created as invalid,
which is confusing to new users.

Backpatch to 14 (only because of a conflict in 13).

Author: Laurenz Albe <laurenz.albe@cybertec.at>
Reported-by: Lauren Fliksteen <dancernerd32@gmail.com>
Reviewed-by: Rajakavitha Kodhandapani <krajakavitha@gmail.com>
Discussion: https://postgr.es/m/165290238488.670.7500177735573254738@wrigleys.postgresql.org