[Security:StackManagement:AIassistantForAdvancedSettings] New index, New Document, system prompt, quick prompt are all announced incorrectly on AI assistant corresponding tabs

[bhavyarm]

Description
When user clicks on any of flyouts for New index, New Document, system prompt, quick prompt - they are all announced as "...you are in a modal dialog.." without the title. This doesn't give any context to non-sighted user.

Preconditions
Security->Stack Management-> AI assistant for advanced settings
Click on different flyouts on different tabs

Steps to reproduce

1. Navigate to Security-> Stack management->AI assistant for advanced settings
2. Run voiceover
3. Click on system prompts tab -> system prompt
4. Kibana announces the system prompt flyout as "....you are in a modal dialog..."
5. Click on quick prompts tab -> quick prompt
6. Kibana announces the quick prompt flyout as "....you are in a modal dialog..."
7. Click on Knowledge base ->new index or new document
8. Kibana announces these flyouts as "...you are in a modal dialog.."

Kibana Version: 9.2.0

OS: OS X

Browser: Chrome latest

**WCAG or Vendor Guidance **

• Understanding SC 1.3.1: Info and Relationships (Level A) (https://www.w3.org/WAI/WCAG21/Understanding/info-and-relationships.html)

Related to: https://github.com/elastic/kibana-team/issues/1773

[elasticmachine]

Pinging @elastic/security-solution (Team: SecuritySolution)