[VULN-649] ci: Remove deprecated scan workflow

[theMickster]

🎟️ Tracking

https://bitwarden.atlassian.net/browse/VULN-649

📔 Objective

Removes the deprecated scan.yml GitHub Actions workflow.

[github-actions]

🤖 Bitwarden Claude Code Review

Overall Assessment: APPROVE

This PR removes the deprecated scan.yml GitHub Actions workflow, which previously ran Checkmarx SAST scanning. The change is tracked under VULN-649, indicating AppSec ownership of the deprecation decision. I verified the deletion is complete — no other workflows, scripts, or files in the repository reference scan.yml, the Checkmarx workflow, the check-run job, or the Scan workflow name. No issues found.

Code Review Details

No actionable findings.

[audreyality]

📝 BIT testing has become unstable recently. That's not material to this change, but I merged up from main (where they're fixed) for good measure.