Change log for PROOFPOINT_SENDMAIL_SENTRION

Date Changes
2026-07-17 Enhancement:
- Proofpoint Sendmail Sentrion product was announced End Of Life, and therefore the prebuilt parser won't be updated. We recommend using the GitHub community version of this parser instead (https://github.com/chronicle/content-hub/tree/main/content/parsers/third_party/community/PROOFPOINT_SENDMAIL_SENTRION).
2024-06-05 Enhancement:
- Mapped subject to network.email.subject.
2024-05-22 - Added a Grok pattern over message to parse a new log type.
- Added a Grok over kv_data to extract the field subject.
- Mapped subject to security_result.detection_fields.
2024-03-07 - Newly created parser.