Update API docs.

public/api/wekan.html

@@ -10041,7 +10041,7 @@ System.out.println(response.toString());
 <td>body</td>
 <td>string</td>
 <td>false</td>
-<td>the assignee IDs list of the new card</td>
+<td>the array of maximum one ID of assignee of the new card</td>
 </tr>
 <tr>
 <td>» title</td>
@@ -14335,7 +14335,7 @@ UserSecurity
 <td>[string]|null</td>
 <td>false</td>
 <td>none</td>
-<td>who assignees of the card (user IDs)</td>
+<td>who is assignee of the card (user ID), maximum one ID of assignee in array.</td>
 </tr>
 <tr>
 <td>receivedAt</td>

public/api/wekan.yml

@@ -1276,7 +1276,7 @@ paths:
         - name: assignees
           in: formData
           description: |
-            the assignee IDs list of the new card
+            the array of maximum one ID of assignee of the new card
           type: string
           required: false
         - name: title
@@ -2367,7 +2367,8 @@ definitions:
         x-nullable: true
       assignees:
         description: |
-           who assignees of the card (user IDs)
+           who is assignee of the card (user ID),
+           maximum one ID of assignee in array.
         type: array
         items:
           type: string