Add parent_ids to article request schemas in Preview spec (#478)

* Add parent_ids to article request schemas in Preview spec

Add parent_ids (array of integers) to create_article_request and
update_article_request schemas, and include parent_ids in the POST and
PUT /articles request examples.

This complements PR #448 which added parent_ids to response schemas,
and reflects the write-side changes from intercom/intercom#499615
(gated on RemoveArticleParentIdAndParentType versioned change).

Existing parent_id/parent_type fields are retained — they still
function as inputs when parent_ids is not provided.

* Update api.intercom.io.yaml

Remove references to "sections"

Author: ib-skoric

descriptions/0/api.intercom.io.yaml

@@ -1356,6 +1356,8 @@ paths:
                   state: published
                   parent_id: 145
                   parent_type: collection
+                  parent_ids:
+                  - 145
                   translated_content:
                     fr:
                       title: Merci pour tout
@@ -1545,6 +1547,9 @@ paths:
                 value:
                   title: Christmas is here!
                   body: "<p>New gifts in store for the jolly season</p>"
+                  parent_ids:
+                  - 18
+                  - 19
               article_not_found:
                 summary: Article Not Found
                 value:
@@ -19279,7 +19284,7 @@ components:
           example: http://intercom.test/help/en/articles/3-default-language
         parent_ids:
           type: array
-          description: The ids of the article's parent collections or sections. An
+          description: The ids of the article's parent collections. An
             article without this field stands alone.
           items:
             type: integer
@@ -22108,6 +22113,15 @@ components:
           type: string
           description: The type of parent, which can either be a `collection` or `section`.
           example: collection
+        parent_ids:
+          type: array
+          description: The ids of the article's parent collections.
+            An article without this field stands alone.
+          items:
+            type: integer
+          example:
+          - 18
+          - 19
         translated_content:
           "$ref": "#/components/schemas/article_translated_content"
         folder_id:
@@ -28256,6 +28270,15 @@ components:
           type: string
           description: The type of parent, which can either be a `collection` or `section`.
           example: collection
+        parent_ids:
+          type: array
+          description: The ids of the article's parent collections.
+            An article without this field stands alone.
+          items:
+            type: integer
+          example:
+          - 18
+          - 19
         translated_content:
           "$ref": "#/components/schemas/article_translated_content"
         folder_id: