Update security-center-about.mdx

add limitation to highlight need for sdk 1.9.0 or higher

Author: AmberAlston

docs/vendor/security-center-about.mdx

@@ -16,6 +16,7 @@ The Security Center is powered by Replicated’s [SecureBuild](https://securebui
 * The Security Center is Alpha. The features and functionality of the Security Center are subject to change.
 * Access to the Security Center Alpha requires a feature flag be turned on for your team. For more information, reach out to your Replicated account representative.
 * Security Center reporting is available only for Embedded Cluster and Helm CLI installations. It is not available for kURL installations or for KOTS installations in an existing cluster.
+* Display and reporting of Embedded Cluster images requires the [Replicated SDK version 1.9.0](/release-notes/rn-replicated-sdk#190) or later.
 
 ## Security Center Interfaces