howto/postgresql: update install procedure

Marking this as tested since I was able to follow it successfully once I
figured out *where* to grab the autogenerated password.

howto/postgresql.md

@@ -1126,9 +1126,6 @@ also applies here.
 
 ## Installation
 
-WARNING: this procedure is possibly incomplete, and has been followed
-successfully only once, in tpo/tpa/team#40770.
-
 PostgreSQL servers are installed by hand on TPO servers, from Debian
 packages. For example, in Debian bullseye:
 
@@ -1136,11 +1133,12 @@ packages. For example, in Debian bullseye:
 
 To ensure backups are properly performed, the server must also have
 the `profile::postgres` class. The storage backup server also needs
-`REPLICATION` access to make full backups. 
+`REPLICATION` access to make full backups. To set this up, follow the
+steps below:
 
 First, add the Puppet class to the new server, and run puppet on that
 server and on the storage server (currently `bungei`) to create the
-replication password.
+replication password (stored in trocla).
 
 Then, create a backup user, using that password: