fix: address code review - clarify plaintext note, fix misleading template ternary

Agent-Logs-Url: https://github.com/christianlouis/dmarq/sessions/0c63851e-a69a-4a76-8dd8-25618e825b8c

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

backend/app/services/gmail_client.py

@@ -11,7 +11,7 @@ import base64
 import email
 import json
 import logging
-from typing import Any, Dict, List, Optional, Tuple
+from typing import Any, Dict, List, Optional
 from urllib.parse import urlencode
 
 import httpx
@@ -295,10 +295,7 @@ class GmailClient:
         """
         try:
             msg_data = (
-                service.users()
-                .messages()
-                .get(userId="me", id=msg_id, format="raw")
-                .execute()
+                service.users().messages().get(userId="me", id=msg_id, format="raw").execute()
             )
         except HttpError as exc:
             logger.error("Gmail API: failed to fetch message %s: %s", msg_id, exc)