Dovecot: Raise mail_max_userip_connections.

We're reaching the limit frequently. Either because I have multiple
clients on the same machine or because I have even more clients on the
same network behind the same IP address.

dovecot/patch.diff

@@ -194,3 +194,12 @@
  
  # If you need to set multiple mailbox locations or want to change default
  # namespace settings, you can do it by defining namespace sections.
+--- conf.d/20-imap.conf	2020-12-22 13:26:52.000000000 +0000
++++ conf.d/20-imap.conf	2022-12-05 07:33:47.876334736 +0000
+@@ -95,5 +95,5 @@
+ 
+   # Maximum number of IMAP connections allowed for a user from each IP address.
+   # NOTE: The username is compared case-sensitively.
+-  #mail_max_userip_connections = 10
++  mail_max_userip_connections = 15
+ }