Cylc Check Version: Broken for Cylc 7 platform settings

[wxtim]

Reproducible Example

# global.cylc
[platforms]
    [[myplatform]]
        hosts = remote_host

# flow.cylc
[runtime]
    [[foo]]
        [[[remote]]]
            host = remote_host

cylc check-version <workflow>
# returns nothing, doesn't check `remote_host`

Cause

This line is getting a list of platform names from the runtime, but ignoring other runtime settings:

cylc-flow/cylc/flow/scripts/check_versions.py

Line 92 in 33788b3

platforms = {