.ostc-ci: allow freertos-armv5 to fail

This build is reliably failing to fetch when invoked without download
cache constructed earlier. I've filed an issue to track this
but this blocks the auto-scaling CI system from going to production

Related-To: https://git.ostc-eu.org/OSTC/OHOS/meta-ohos/-/issues/132


Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@huawei.com>