chore(docs): Updated API Reference (#6831)

Automated changes by [create-pull-request](https://github.com/peter-evans/create-pull-request) GitHub action

Co-authored-by: Oli Juhl <59018053+olivermrbl@users.noreply.github.com>
Co-authored-by: Shahed Nasser <27354907+shahednasser@users.noreply.github.com>

www/apps/api-reference/specs/admin/paths/admin_variants.yaml

@@ -47,6 +47,25 @@ get:
       schema:
         type: number
         default: '100'
+    - in: query
+      name: order
+      description: >-
+        The field to sort the data by. By default, the sort order is ascending.
+        To change the order to descending, prefix the field name with `-`.
+      schema:
+        type: string
+    - in: query
+      name: manage_inventory
+      description: Filter product variants by whether their inventory is managed or not.
+      schema:
+        type: boolean
+    - in: query
+      name: allow_backorder
+      description: >-
+        Filter product variants by whether they are allowed to be backordered or
+        not.
+      schema:
+        type: boolean
     - in: query
       name: cart_id
       style: form