docs: add SSO free for up to 5 users info block to security.md

Author: berri-teddy

security.md

@@ -12,6 +12,11 @@
 - For installation and configuration, see: [Self-hosting guided](https://docs.litellm.ai/docs/proxy/deploy)
 - **Telemetry** We run no telemetry when you self host LiteLLM
 
+
+:::info
+✨ SSO is free for up to 5 users. After that, an enterprise license is required. [Get Started with Enterprise here](https://www.litellm.ai/enterprise)
+:::
+
 ### LiteLLM Cloud
 
 - We encrypt all data stored using your `LITELLM_MASTER_KEY` and in transit using TLS.