guides/quick: Minor tweaks to quick configuration example

Reorder the settings to make more sense. Update comments. Remove the
lower-filter from %{user}, because the default auth_username_format
already lowercases the user. Add dovecot_*_version settings. Remove
userdb passwd, since nothing from it is actually used.

Author: sirainen

docs/core/config/guides/quick.md

@@ -26,35 +26,31 @@ You need to create group `vmail` and user `vmail`.
 
 ::: code-group
 ```[dovecot.conf]
-mail_home = /srv/mail/%{user | lower}
+# Start new configs with the latest Dovecot version numbers here:
+dovecot_config_version = 3.1.0
+dovecot_storage_version = 3.1.0
+
+mail_home = /srv/mail/%{user}
 mail_driver = sdbox
 mail_path = ~/Mail
 
+mail_uid = vmail
+mail_gid = vmail
 ## this is sometimes needed
-#first_valid_uid = uid-of-vmail-user
+#first_valid_uid = uid-number-of-vmail-user
 
-# if you want to use system users
-passdb pam {
-  driver = pam
+namespace inbox {
+  inbox = yes
+  separator = /
 }
 
-userdb passwd {
-  driver = passwd
-  use_worker = yes
-  fields {
-    uid = vmail
-    gid = vmail
-  }
+# Use system users:
+passdb pam {
 }
 
-ssl=yes
+ssl = yes
 ssl_cert_file = /path/to/cert.pem
 ssl_key_file = /path/to/key.pem
-
-namespace {
-  inbox = yes
-  separator = /
-}
 ```
 :::