SOLR-16705: Remove useless Zookeeper checks

[psalagnac]

https://issues.apache.org/jira/browse/SOLR-16705

Description

In class ShardLeaderElectionContext, call to method areAllReplicasParticipating() is useless and we ignore the returned value.

Solution

Remove some useless code with ZK calls in shard leader election.

Tests

No test added for this.

Checklist

Please review the following and check all that apply:

• I have reviewed the guidelines for How to Contribute and my code conforms to the standards described there to the best of my ability.
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• I have developed this patch against the main branch.
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• I have added tests for my changes.
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[markrmiller]

areAllReplicasParticipating

This should have been made obsolete with the introduction of the LIR term work. Which is probably why the return value is not used, but obviously the call wasn't removed.

[psalagnac]

Hi @markrmiller,
Thanks for looking into this.
Is this change good to be merged? Is something else required?
Thanks

[murblanc]

@markrmiller @noblepaul I plan to merge this 5 days from now (April 9th) if there's no disagreement