docs: access Zookeeper constants from ZooKeeper.constants

[maharjanraj]

Update Readme to use constants from Zookeeper.constants.*

Description

Since accessing constants directly from Zookeeper is deprecated, it is necessary to update the readme document to use constants from ZooKeeper.constants.*

Motivation and Context

Readme document still uses a deprecated way to access Zookeeper constants.

How Has This Been Tested?

Not needed

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Readme document

Checklist:

• I have read the code of conduct.
• I have read the contributing guide.
• I have updated the documentation accordingly (if applicable).

[DavidVujic]

Thank you! 👏