Simplify admin hash in the secret

[rileyai-dev]

What this PR does / why we need it:

This PR is for simplifying the adminHash in the secret

Special notes for your reviewer:

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.

• [x] Chart Version bumped
• [x] e2e tests pass
• [x] Variables are documented in the README.md

[willholley]

The changes look good. However, I think it would be a breaking change for anybody that followed the instructions at https://github.com/apache/couchdb-helm/tree/main/couchdb#installing-the-chart to create their own admin secret containing a password.ini key. Probably this is a very small number of users, but it strictly should warrant a major chart version bump given Helm assumes SemVer 2.

Sorry not to have twigged this sooner - do you think you could bump the version to 4.0.0 and add a brief migration section under the version in NEWS.md?