Keep email runtime configuration out of Vault

infra/local/scripts/start-service.sh

@@ -2,9 +2,6 @@
 set -eu
 umask 077
 if [ "$SXCHNGE_SERVICE" = notifications ]; then
-    printf '%s\n' "$EMAIL_CONFIG" > /run/sxchnge/email.yml
-    unset EMAIL_CONFIG
-    cat /etc/sxchnge/notifications.yml /run/sxchnge/email.yml > /run/sxchnge/config.yml
-    exec service -config.file=/run/sxchnge/config.yml
+    exec service -config.file=/etc/sxchnge/notifications.yml
 fi
 exec service -config.file=/etc/sxchnge/bff.yml