Remove depSASTer triggered pipeline

What does this MR do and why?

DepSASTer Removal (gitlab-com/gl-security/product-security&10 - closed) revealed that, at present, depSASTer is not delivering value and instead adds almost entirely unhelpful noise.

This MR removes depSASTer from the gitlab-org/gitlab pipeline.

• Identify where depSASTer is referenced: https://gitlab.com/search?search=depsaster&nav_source=navbar&project_id=278964&group_id=9970&search_code=true&repository_ref=master
  • Remove the trigger pipeline job from .gitlab/ci/static-analysis.gitlab-ci.yml
  • Remove its boolean in .gitlab-ci.yml
  • Remove the rules from .gitlab/ci/rules.gitlab-ci.yml

MR acceptance checklist

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Related to #460792 (closed)