Update helm chart docs for private registry params #43720

What do you see as an issue?

Update the private registry params with more meaningful descriptions, in the Parameters reference doc for Airflow Helm chart.

Refer Slack thread for context: https://apache-airflow.slack.com/archives/CCQ7EGB1P/p1730830360500959?thread_ts=1730751844.244849&cid=CCQ7EGB1P

Solving the problem

Use more meaningful description for the parameters.

Anything else

No response

Are you willing to submit PR?

• Yes I am willing to submit a PR!

Code of Conduct

• I agree to follow this project's Code of Conduct