Change heading level of case insensitive matching fragment

[blvckcoffee]

Description

• Changes the heading level of the jdbc-case-insensitive-matching.fragment to be a direct subheading of Configuration.

Additional context and related issues

*This fragment is currently nested under the jdbc-procedures.fragment but does not seem to be related to that section. If it's just another configuration property, and isn't a type of procedure, we should just nest it under Configuration.

• Heading was previously changed in Clean up join pushdown docs for JDBC connectors #11967

Release notes

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# Section
* Fix some things. ({issue}`issuenumber`)