[VOTE] PIP-122: Change loadBalancer default loadSheddingStrategy to ThresholdShedder

[Hang Chen]

This is the voting thread for PIP-122. It will stay open for at least 48
hours.

https://github.com/apache/pulsar/issues/13340

Pasted below for quoting convenience.

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### Motivation
The ThresholdShedder load balance policy since Pulsar 2.6.0 by
https://github.com/apache/pulsar/pull/6772. It can resolve many load
balance issues of `OverloadShedder` and works well in many Pulsar
production clusters.

In Pulsar 2.6.0, 2.7.0, 2.8.0 and 2.9.0, Pulsar's default load balance
policy is `OverloadShedder`.

I think it's a good time for 2.10 to change default load balance
policy to `ThresholdShedder`, it will make throughput more balance
between brokers.

### Proposed Changes
In 2.10 release，for `broker.conf`, change
`loadBalancerLoadSheddingStrategy` from
`org.apache.pulsar.broker.loadbalance.impl.OverloadShedder` to
`org.apache.pulsar.broker.loadbalance.impl.ThresholdShedder`