check-schemas: Add list of deprecated events in OpenAPI documentation.

In commit 268f858f3, we removed the "realm_filters" event from the
schemas that we test in `zerver/lib/event_schemas.py`, but the event
is still documented (as deprecated) in the api/get-events doc.

Updates `tools/check_schemas` to not print a warning for an event
schema in the OpenAPI documentation if it's include in the list of
deprecated events list.

tools/check-schemas

@@ -74,7 +74,6 @@ EXEMPT_OPENAPI_NAMES = [
     "message_event",
     # tuple handling
     "muted_topics_event",
-    "realm_filters_event",
     # bots, delivery_email, profile_data
     "realm_user_add_event",
     # OpenAPI is incomplete
@@ -84,6 +83,12 @@ EXEMPT_OPENAPI_NAMES = [
     "reaction_remove_event",
 ]
 
+# This is a list of events still documented in the OpenAPI that
+# are deprecated and no longer checked in event_schema.py.
+DEPRECATED_EVENTS = [
+    "realm_filters_event",
+]
+
 
 def get_event_checker(event: Dict[str, Any]) -> Optional[Callable[[str, Dict[str, Any]], None]]:
     name = event["type"]
@@ -192,6 +197,7 @@ def validate_openapi_against_event_schema() -> None:
         name += "_event"
 
         if not hasattr(event_schema, name):
+            if name not in DEPRECATED_EVENTS:
                 print("WARNING - NEED SCHEMA to match OpenAPI", name)
             continue