Add reference to compliance page update (#1501)

Author: schavis

content/vault/v1.21.x/content/docs/enterprise/fips/index.mdx

@@ -12,7 +12,15 @@ description: >-
 The [Federal Information Processing Standard](https://www.nist.gov/federal-information-standards-fips)
 is a cryptography-focused certification standard for U.S. Government usage.
 
-Hashicorp's Vault Enterprise supports the modes of FIPS compliance documented below.
+## FIPS 140-3 attestation
+
+[Leidos](https://www.leidos.com/capabilities/technology-certifications) has
+attested that Vault Enterprise 1.19.4+ with FIPS Enabled is conformant with the
+Federal Information Processing Standard (FIPS) 140-3 standards.
+
+You can read the details about how Vault supports FIPS 140-3 in the
+[FIPS 140-3 attestation letter issued by Leidos](https://www.hashicorp.com/vault-compliance).
+
 
 ## FIPS 140-3 inside