When PostgreSQL starts, we see the following errors in the logs:
```
mkdir:
cannot create directory ‘/tmp/appsmith/postgres-stats’
: Permission denied
```
And then this over and over again:
```
postgres stdout | 2023-09-19 15:34:34.504 UTC [1759] LOG: could not open temporary statistics file "/tmp/appsmith/postgres-stats/global.tmp": No such file or directory
```
The problem is that in `postgres.conf`, we set `user=postgres`, which
doesn't have access to create things in `/tmp`.
This PR removes this configuration and lets the default be, which will
be a temp folders _under_ the data directory.
