feat(restic): Use RESTIC_PASSWORD_FILE instead of RESTIC_PASSWORD

roles/restic/templates/restic.service.j2

@@ -8,7 +8,7 @@ WorkingDirectory={{ restic_systemd_working_directory }}
 SyslogIdentifier={{ restic_systemd_syslog_identifier }}
 
 Environment=RESTIC_REPOSITORY={{ restic_repo_url }}
-Environment=RESTIC_PASSWORD={{ restic_repo_password }}
+Environment=RESTIC_PASSWORD_FILE={{ restic_password_file_path }}
 {% for kv in restic_complete_environment | dict2items %}
 Environment={{ kv.key }}={{ kv.value }}
 {% endfor %}