Move OnFailure to [Unit] section

OnFailure directive must be in [Unit], not [Service], for systemd
user services to recognize it.

Changes:
- Move OnFailure from [Service] to [Unit] in email_forwarder.service

email_forwarder.service

@@ -1,12 +1,11 @@
 [Unit]
 Description=Email Forwarder
+OnFailure=email_forwarder-fail-notify.service
 
 [Service]
-WorkingDirectory=${PROJECT_DIR}
 ExecStart=${PROJECT_DIR}/venv/bin/python -m email_forwarder
 EnvironmentFile=${PROJECT_DIR}/.env
 ExecStartPost=/bin/sh -c '/usr/bin/curl -fsS --retry 3 "$UPTIME_SUCCESS_URL"'
-OnFailure=email_forwarder-fail-notify.service
 
 [Install]
 WantedBy=default.target