Add kotlin support to spotbugs-sast job

What does this MR do?

In gitlab-org/security-products/analyzers/spotbugs!93 (merged), kotlin support was added to the spotbugs SAST analyzer. This MR adds the .kt file extension to the detection rules for that analyzer, enabling native support for kotlin as part of GitLab's SAST offering.

Related issues and MRs

• #36783 (closed)
• gitlab-org/security-products/analyzers/spotbugs!93 (merged)

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Does this MR meet the acceptance criteria?

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