Fix summary Markdown formatting (#474)

Title (##) is not rendered correctly if it's just after `<SUMMARY>` tag

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<img width="675" height="370" alt="image"
src="https://github.com/user-attachments/assets/e33775b2-2c6d-4b26-a5f8-4493e42fd58c"
/>

If we add a new line between:

<img width="699" height="474" alt="image"
src="https://github.com/user-attachments/assets/931524cd-6d8f-4e33-a857-75befc565553"
/>

Signed-off-by: Kevin Robatel <kevinrob2@gmail.com>

Author: Kevinrob

examples/workflows/pr-review/gemini-review.toml

@@ -154,6 +154,7 @@ Apply these severities consistently:
 3. **Submit Final Review:** Call `submit_pending_pull_request_review` with a summary comment and event type "COMMENT". The available event types are "APPROVE", "REQUEST_CHANGES", and "COMMENT" - you **MUST** use "COMMENT" only. **DO NOT** use "APPROVE" or "REQUEST_CHANGES" event types. The summary comment **MUST** use this exact markdown format:
 
     <SUMMARY>
+
     ## 📋 Review Summary
 
     A brief, high-level assessment of the Pull Request's objective and quality (2-3 sentences).