[Security Solution] Disable O11y features in Security Serverless project (elastic#203990)

## Summary

Fixes 
- elastic#202532


`Observability` feature `Inventory` should not appear in `Security`
serverless project


|Before|After|
|--|--|

|![image](https://github.com/user-attachments/assets/90c35b55-d217-4afe-a7f4-78324c4e62c4)|![image](https://github.com/user-attachments/assets/9c659fa8-1e23-4696-b4ee-27d9c61ffafc)|

Author: logeekal

config/serverless.security.yml

@@ -10,6 +10,7 @@ xpack.observabilityAIAssistant.enabled: false
 xpack.search.notebooks.enabled: false
 xpack.searchPlayground.enabled: false
 xpack.searchInferenceEndpoints.enabled: false
+xpack.inventory.enabled: false
 
 ## Fine-tune the security solution feature privileges. Also, refer to `serverless.yml` for the project-agnostic overrides.
 xpack.features.overrides: