Fix v4 branch

What does this MR do?

The v4 branch is used to apply bug fixes to version 4 of semgrep so we can continue to support users still on GitLab v16.

However, the v4 branch can not be built because the VET projects is relies on have been removed.

This MR applied the following changes from the main branch:

• Remove VET as a post-analyser from semgrep (!415 - merged) • Julian Thome • 17.1
• Remove confusing comment (!419 - merged) • Julian Thome • 17.1

This update will allow us to backport bug fixes made on main to v4.

What are the relevant issue numbers?

Test and fix all remote SAST remote configurati... (gitlab-org/gitlab#458845 - closed) • Craig Smith • 17.2

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests updated/added for this feature/bug
• Job definition updated, if necessary
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• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer