Document display_as parameter behavior for subject field (#318)

Author: marcmlc

descriptions/0/api.intercom.io.yaml

@@ -6196,7 +6196,7 @@ paths:
       - name: display_as
         in: query
         required: false
-        description: Set to plaintext to retrieve conversation messages in plain text.
+        description: Set to plaintext to retrieve conversation messages in plain text. This affects both the body and subject fields.
         example: plaintext
         schema:
           type: string
@@ -6450,7 +6450,7 @@ paths:
       - name: display_as
         in: query
         required: false
-        description: Set to plaintext to retrieve conversation messages in plain text.
+        description: Set to plaintext to retrieve conversation messages in plain text. This affects both the body and subject fields.
         example: plaintext
         schema:
           type: string