docs: state the embed-shape constraint instead of its history

The pinning tests are the real contract; the deleted builders are not
something a future reader can compare against.

Author: Zingzy

infrastructure/ops_notify.py

@@ -60,8 +60,9 @@ class DiscordOpsNotifier:
     """Discord implementation — routes each notification to its channel
     (contact vs reports) and builds the embeds.
 
-    Embed structures are preserved exactly from the previous per-service
-    builders (originally ``utils/contact_utils.py``).
+    Embed shapes are pinned by the integration tests (test_contact /
+    test_reports run this class over a capturing HTTP fake): change a
+    field here and a test breaks.
     """
 
     def __init__(