Docs: Update SAST_JAVA_VERSION values

What does this MR do?

In GitLab 15.0 we'll bump the SpotBugs analyzer version to 4.0, which brings in a new set of supported versions for SAST_JAVA_VERSION.

We need some way of documenting both the new values and the old values. I picked an approach here but am very open to suggestions.

Related issues

SAST Deprecation: Out-of-the-box Java 8 support... (#352549 - closed)

Remove JDK 8 support out of the box (gitlab-org/security-products/analyzers/spotbugs!138 - merged)

Update SAST analyzer major versions (!87292 - merged)

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