ci: Keep Trivy cache up-to-date on default branch

[SanjayVas]

See https://github.com/aquasecurity/trivy-action?tab=readme-ov-file#updating-caches-in-the-default-branch

[wfa-reviewable]

This change is 

[stevenwarejones]

Reviewed all commit messages.
Reviewable status: 0 of 2 files reviewed, 1 unresolved discussion (waiting on @SanjayVas)

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.github/workflows/scan-images.yml line 99 at r1 (raw file):

        uses: aquasecurity/[email protected]
        env:
          TRIVY_SKIP_DB_UPDATE: true

why would we skip updating the vulnerability db?

[SanjayVas]

Reviewable status: 0 of 2 files reviewed, 1 unresolved discussion (waiting on @stevenwarejones)

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.github/workflows/scan-images.yml line 99 at r1 (raw file):

Previously, stevenwarejones (Steven Ware Jones) wrote…

why would we skip updating the vulnerability db?

The idea is to use the cached versions rather than having the Trivy application attempt to download the DBs. The link in the PR description explains this.

[stevenwarejones]

Reviewed 2 of 2 files at r1.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @SanjayVas)

[SanjayVas]

Dismissed @stevenwarejones from a discussion.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @SanjayVas)