add data retention policy

Author: forstisabella

src/_data/sidenav/main.yml

@@ -591,6 +591,8 @@ sections:
       title: Consent in Reverse ETL
     - path: /privacy/consent-management/consent-faq
       title: Consent FAQs
+  - path: /privacy/data-retention-policy
+    title: Data Retention and Deletion Policy
   - path: /privacy/account-deletion
     title: Account & Data Deletion
   - path: /privacy/hipaa-eligible-segment