Clarify that /context always returns 'event' even if limit is zero

Signed-off-by: Sumner Evans <me@sumnerevans.com>

data/api/client-server/event_context.yaml

@@ -57,7 +57,10 @@ paths:
           type: integer
           name: limit
           description: |-
-            The maximum number of events to return. Default: 10.
+            The maximum number of context events to return. The limit applies
+            to the sum of the `events_before` and `events_after` arrays. The
+            requested event ID is always returned in `event` even if `limit` is
+            0. Default: 10.
           x-example: 3
         - in: query
           name: filter