[improve][zk] Upgrade ZooKeeper to 3.9.6 - #26750

Motivation

Keep Pulsar on the ZooKeeper 3.9 maintenance line while incorporating the updates in 3.9.6.

Modifications

• Update the shared ZooKeeper version from 3.9.5 to 3.9.6, including its test artifact and transitive zookeeper-jute dependency.
• Update the server distribution license inventory for zookeeper-jute 3.9.6.

Verifying this change

• ./gradlew checkBinaryLicense — passed.
• Tests were not run, as requested. No additional Gradle checks were run.
• Make sure that the change passes the CI checks.

Does this pull request potentially affect one of the following parts:

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment