ART-11093 use group arches to get rhcos list

[Ximinhan]

When get rhcos arches, use group config arches instead of parameter arches for nightly.
https://redhat-internal.slack.com/archives/GDBRP5YJH/p1734708885038709?thread_ts=1734705090.164539&cid=GDBRP5YJH

[openshift-ci]

@Ximinhan: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/security	b8dbe04	link	false	/test security

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[lgarciaaco]

/approve

[openshift-ci]

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