Minor improvements to ClickHouse doc

[tangjiangling]

Previously, ClickHouse documentation did not explicitly state:

1. what parameters users can set via connection-url
2. how to secretly set connection-password

So this pr:

• Reference to the parameters supported by connection-url
• Reference to use secret way to configure connection-password

Description

Is this change a fix, improvement, new feature, refactoring, or other?

Doc improvements.

Is this a change to the core query engine, a connector, client library, or the SPI interfaces? (be specific)

ClickHouse doc.

How would you describe this change to a non-technical end user or system administrator?

N/A.

Related issues, pull requests, and links

Fixes #13527

Documentation

(x) Sufficient documentation is included in this PR.

Release notes

(x) No release notes entries required.

[tangjiangling]

TODO: We also need to check if other JDBC connectors have the same issue.

[mosabua]

TODO: We also need to check if other JDBC connectors have the same issue.

Feel free to do so .. lots of other connectors will have that snippet already.

[hashhar]

Looks good to me.

We should probably have similar boilerplate in consistent language in all JDBC connector docs. cc: @mosabua

[hashhar]

@tangjiangling I'm merging this one as it is. Please feel free to submit additional PR for other JDBC connectors. Thanks for the improvement.