docs([tokio-]postgres/config): fix examples for unix socket paths

[transcaffeine]

The commonly used location for sockets is /run/{service}, with /var/lib/{service} containing the actual data from the service.

[sfackler]

That may be true, but the commonly used location (in e.g. Ubuntu 24.04) for the Postgres socket is /var/lib/{service}.

[leona-ya]

On a new Ubuntu 24.04 (with the standard repos) on a clean install I get the postgresql socket in /run/postgresql (equivalent to /var/run/postgresql):

root@testubuntu01:~# ls /var/run/postgresql/ -al
total 8
drwxrwsr-x  2 postgres postgres  100 Mar  2 20:21 .
drwxr-xr-x 31 root     root     1080 Mar  2 20:21 ..
srwxrwxrwx  1 postgres postgres    0 Mar  2 20:21 .s.PGSQL.5432
-rw-------  1 postgres postgres   70 Mar  2 20:21 .s.PGSQL.5432.lock
-rw-r--r--  1 postgres postgres    6 Mar  2 20:21 16-main.pid
root@testubuntu01:~# uname -a
Linux testubuntu01 6.8.0-52-generic #53-Ubuntu SMP PREEMPT_DYNAMIC Sat Jan 11 00:06:25 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux
root@testubuntu01:~# cat /etc/os-release
PRETTY_NAME="Ubuntu 24.04.1 LTS"
NAME="Ubuntu"
VERSION_ID="24.04"
VERSION="24.04.1 LTS (Noble Numbat)"
VERSION_CODENAME=noble
ID=ubuntu
ID_LIKE=debian

[sfackler]

Sorry, yeah I misread /var/run as /var/lib. I'd prefer this use /var/run/postgresql instead of just /run to match with how psql is built:

root@80cc00b8042c:/# psql
psql: error: connection to server on socket "/var/run/postgresql/.s.PGSQL.5432" failed: No such file or directory
        Is the server running locally and accepting connections on that socket?
```

[transcaffeine]

@sfackler i changed the paths to be all /var/run/postgresql :)