style: Adjust Markdown headings for structure and conciseness

This commit refines the Markdown heading structure in the output of
`scripts/gha/get_pr_review_comments.py` for improved readability
and document hierarchy.

Changes include:
- The main output title "Review Comments" is now an H1 heading.
- Each comment's attribution line (user, ID) is now an H2 heading.
- Section headings within each comment, "Context" (formerly "Diff
  Hunk Context") and "Comment" (formerly "Comment Body"), are now
  H3 headings.

These changes make the script's output more organized and easier to
navigate when rendered as Markdown.

Author: google-labs-jules[bot]

scripts/gha/get_pr_review_comments.py

@@ -113,7 +113,7 @@ def main():
         return
 
     latest_created_at_obj = None
-    print("\n--- Review Comments ---")
+    print("# Review Comments\n")
     for comment in comments:
         created_at_str = comment.get("created_at")
 
@@ -171,15 +171,15 @@ def main():
         comment_id = comment.get("id")
         in_reply_to_id = comment.get("in_reply_to_id")
 
-        print(f"### Comment by: **{user}** (ID: `{comment_id}`){f' (In Reply To: `{in_reply_to_id}`)' if in_reply_to_id else ''}\n")
+        print(f"## Comment by: **{user}** (ID: `{comment_id}`){f' (In Reply To: `{in_reply_to_id}`)' if in_reply_to_id else ''}\n")
         if created_at_str:
             print(f"*   **Timestamp**: `{created_at_str}`")
         print(f"*   **Status**: `{status_text}`")
         print(f"*   **File**: `{path}`")
         print(f"*   **Line**: `{line_to_display}`") # Label changed from "Line in File Diff"
         print(f"*   **URL**: <{html_url}>\n")
 
-        print("#### Diff Hunk Context:")
+        print("### Context:")
         print("```") # Start of Markdown code block
         if diff_hunk and diff_hunk.strip():
             hunk_lines = diff_hunk.split('\n')
@@ -194,7 +194,7 @@ def main():
             print("(No diff hunk available for this comment)")
         print("```") # End of Markdown code block
 
-        print("#### Comment Body:")
+        print("### Comment:")
         print(body)
         print("\n---")