Updated openstack/openstack
Project: openstack/heat  5e64c52c55cb25d2c1a2d6f19662ca882b3c068c

Amend docs with `immutable` property attribute.

Include warning about updates not being supported for a propety
based on its `immutable` value being True.

Change-Id: I10fe495a2a35429b3d6e254c23ae91732e2e4dd8
Implements: blueprint implement-aws-updates-not-supported