[CI] full-cluster-restart BWC-Test fails because 6.0 is not released yet

[talevy]

link: https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+master+bwc-tests/229/console

error message:

:checkout-6.0:distribution:zip:assemble
:qa:full-cluster-restart:v6.0.0-SNAPSHOT#oldClusterTestCluster#prepareCluster.cleanShared
:qa:full-cluster-restart:v6.0.0-SNAPSHOT#oldClusterTestCluster#node0.clean
:qa:full-cluster-restart:v6.0.0-SNAPSHOT#oldClusterTestCluster#node0.checkPrevious SKIPPED
:qa:full-cluster-restart:v6.0.0-SNAPSHOT#oldClusterTestCluster#node0.stopPrevious SKIPPED
:qa:full-cluster-restart:v6.0.0-SNAPSHOT#oldClusterTestCluster#node0.extract FAILED
Cannot expand ZIP '/var/lib/jenkins/workspace/elastic+elasticsearch+master+bwc-tests/distribution/bwc/build/bwc/checkout-6.0/distribution/zip/build/distributions/elasticsearch-6.0.0-SNAPSHOT.zip' as it does not exist.

reproduce with:

gradle :qa:full-cluster-restart:bwcTest

Looks like this is somewhat expected until 6.0 is released, since the actual artifact is 6.0-beta2-SNAPSHOT

[talevy]

Closing in favor of #26066