Bugfix to remove apiVersion from embedded routes in Route Table

[ninjarobot]

The changes in this PR are as follows:

• Route Tables: Fix bug where embedded routes should only serialize properties.

I have read the contributing guidelines and have completed the following:

• [x] Tested my code end-to-end against a live Azure subscription.
• [ ] Updated the documentation in the docs folder for the affected changes.
• [x] Written unit tests against the modified code that I have made.
• [x] Updated the release notes with a new entry for this PR.
• [x] Checked the coding standards outlined in the contributions guide and ensured my code adheres to them.

If I haven't completed any of the tasks above, I include the reasons why here: No documentation update since this is an internal bug fix.

routeTable {
    name "test-rt"
    add_routes [
        route {
            name "virtual-net1"
            addressPrefix "100.72.16.0/24"
            nextHopIpAddress "100.72.2.53"
        }
        route {
            name "virtual-net2"
            addressPrefix "192.168.100.0/24"
            nextHopIpAddress "100.72.2.53"
        }
    ]
}

[ninjarobot]

@thinkdavid can you please review this minor change so that routes can be nested within the route table? The apiVersion on the nested routes was causing this error:

Could not find member 'apiVersion' on object of type 'Route'. Path 'properties.routes[0].apiVersion'