ISSUE-17918: [Doc] Update the release process about how to release C++ and Python client

[sijie]

Original Issue: apache#17918

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• I searched in the issues and found nothing similar.

What issue do you find in Pulsar docs?

After apache#17724 moves pulsar-client-cpp and pulsar-client-python to new repository, the original release process is no longer valid.

What is your suggestion?

cc @merlimat @BewareMyPower @shibd @RobertIndie

IIRC these two clients have their own release cycle, thus the issue here can be simply to remove the related sections in the current release process and then write the new one in each repo.

Any reference?

No response

Are you willing to submit a PR?

• I'm willing to submit a PR!