config: drop unsupported 'before' field from 12_dbus.service

The local init fork's Service struct does not have a 'before' field
(it supports cmd, args, envs, inherit_envs, type only), and the
deny_unknown_fields attribute makes init panic at boot when it parses
'before':

  init: /etc/init.d/12_dbus.service: unknown field 'before', expected
  one of 'cmd', 'args', 'envs', 'inherit_envs', 'type' in 'service'

The 'before = [13_redbear-sessiond.service]' line was redundant
anyway: 13_redbear-sessiond.service already declares
requires_weak = ['12_dbus.service'], which orders it after dbus.

Fix both redbear-mini.toml and redbear-full.toml.

config/redbear-full.toml

@@ -227,7 +227,6 @@ requires_weak = [
 cmd = "/usr/bin/dbus-daemon"
 args = ["--system", "--nopidfile", "--address=unix:path=/run/dbus/system_bus_socket"]
 type = "oneshot_async"
-before = ["13_redbear-sessiond.service"]
 """
 
 [[files]]

config/redbear-mini.toml

@@ -359,7 +359,6 @@ cmd = "dbus-daemon"
 args = ["--system", "--nopidfile", "--address=unix:path=/run/dbus/system_bus_socket"]
 envs = { DBUS_SYSTEM_BUS_ADDRESS = "unix:path=/run/dbus/system_bus_socket" }
 type = "oneshot_async"
-before = ["13_redbear-sessiond.service"]
 """
 
 [[files]]