Correct jira_update_issue example for assignee format

[eran-rom]

Description

This PR corrects the example JSON provided in the jira_update_issue tool description within src/mcp_atlassian/server.py. The previous example incorrectly showed the assignee value as a dictionary ({"name": "..."}). This was inconsistent with the implementation in IssuesMixin.update_issue, which expects a string identifier (username, email, or account ID) for the assignee.

This incorrect example caused runtime error, AttributeError: 'dict' object has no attribute 'startswith', when the tool was used with the assignee provided as a dictionary. This fix resolves the inconsistency and prevents this error.

Changes

• Corrected the assignee example format in the jira_update_issue tool description (server.py).

Testing

• Unit tests added/updated
• Integration tests passed
• Manual checks performed: Confirmed the fix works when using the jira_update_issue tool via Cursor MCP.

Checklist

• Code follows project style guidelines (linting passes).
• Tests added/updated for changes.
• All tests pass locally.
• Documentation updated (if needed).

[sooperset]

Thanks for catching this inconsistency and providing the fix!