dovecot.service: Update LimitNOFILE=65535

Current value of 8192 is too low for most production setups and it needs
to be changed every time something is deployed. Setting the default to
65535 is enough for most production environments so this would be one
task less when deploying a production platform.

dovecot.service.in

@@ -28,7 +28,7 @@ PrivateDevices=true
 # You can add environment variables with e.g.:
 #Environment='CORE_OUTOFMEM=1'
 # If you have trouble with `Too many open files', increase
-LimitNOFILE=8192
+LimitNOFILE=65535
 # If you want to allow the Dovecot services to produce core dumps, use:
 #LimitCORE=infinity