Update os_image.py (#47222)

The description of the `name` and `id` options are updated to highlight the fact that the `name` (which is required and leads to failures if several images exist with the same name) argument can also contain the image `id`.

+label: docsite_pr

lib/ansible/modules/cloud/openstack/os_image.py

@@ -27,12 +27,12 @@ description:
 options:
    name:
      description:
-        - Name that has to be given to the image
+        - The name of the image when uploading - or the name/ID of the image if deleting
      required: true
    id:
      version_added: "2.4"
      description:
-        - The Id of the image
+        - The ID of the image when uploading an image
    checksum:
      version_added: "2.5"
      description: