doc: Add Dockerfile, Google, OpenAPI to SAST-IaC support list

What does this MR do?

Add Dockerfile, OpenAPI, and Google Deployment Manager support to the list of support IaC scanning formats because the underlying tool (kics) supports them.

Note that Google Deployment Manager doesn't have its own standalone page in the list, but you can filter the All queries list by "Google" for "Tool" and see a number of rules.

I chose not to mention Helm or gRPC because, while they're listed on the kics Platforms page, they don't show up in the queries list. (gRPC has a single entry about capitalization, which doesn't seem defensible as a security offering.)

Related issues

This came up in discussion in !77799 (comment 804730133)

Author's checklist

• Consider taking the GitLab Technical Writing Fundamentals course.
• Follow the:
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  • Style Guide.
• Ensure that the product tier badge is added to topic's h1.
• Request a review based on:
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If you are only adding documentation, do not add any of the following labels:

• ~"frontend"
• ~"backend"
• ~"type::bug"
• ~"database"

These labels cause the MR to be added to code verification QA issues.

Review checklist

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• If the content requires it, ensure the information is reviewed by a subject matter expert.
• Technical writer review items:
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• Ensure a release milestone is set.