[SPARK-48813][SQL][DOCS] Add a notice that mariadb protocol does not apply when the database is MariaDB

[wayneguow]

What changes were proposed in this pull request?

This PR aims to add a notice that mariadb protocol does not apply when the database is MariaDB in sql-data-sources-jdbc.md.

Why are the changes needed?

MariaDBDialect is not implemented currently. If the user uses the jdbc:mariadb protocol, an error will occur，as described in https://issues.apache.org/jira/browse/SPARK-25013. It's better to add a notice that when users get an error, they can get help from the documentation.

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Pass GA.

Was this patch authored or co-authored using generative AI tooling?

[wayneguow]

Gentle ping @HyukjinKwon, currently I am just adding a notice in the docs to give some help for users. Do we need to further throw an exception directly for the jdbc:mariadb protocol in the JdbcDialects.get method? But it's a little bit hardcode. WDYT?

[yaooqinn]

Since we don't have MariaDBDialect to support jdbc:mariadb internally, it belongs to third-party implementations. We don't need this for end-users

[wayneguow]

@yaooqinn Thank you for reviewing mariadb related PRs, I think what you said makes sense, so I will close these.