Remove all usages of `vulnerability_occurrence_pipelines` application code

Context

We are deleting the vulnerability_occurrence_pipelines table in this epic

We have already

• added new columns to use instead of the vulnerability_occurrence_pipelines table
• added application code to populate these new columns
• backfilled these new columns
• rolled out the usage of the new columns with a feature flag

This issue

Now that the feature flag is rolled out, we can remove the feature flag. In addition to removing the FF, we can remove all of the application code referencing the vulnerability_occurrence_pipelines table.

Implementation Plan

• remove usages of the `deprecate_vulnerability_o... (#450801 - closed) • Michael Becker • 17.4
• Remove override for `vulnerability_findings` as... (#451877 - closed) • Michael Becker • 17.4
• Stop writing to the `vulnerability_occurrence_p... (#482623 - closed) • Michael Becker • 17.4
• Remove code that delete rows from the table (#486989 - closed) • Michael Becker • 17.5

The actual model code

After Stop writing to the `vulnerability_occurrence_p... (#482623 - closed) • Michael Becker • 17.4 is complete, we should be clear to delete the actual model code. I'd prefer to do this before the actual migration to drop the table, however that may not be possible

• ee/app/models/vulnerabilities/finding.rb#L43

• ee/spec/models/vulnerabilities/finding_spec.rb#L22

• remove from TODO yamls

  • .rubocop_todo/layout/line_length.yml#L889
  • .rubocop_todo/rspec/context_wording.yml#L485
  • spec/support/rspec_order_todo.yml#L1776

• remove several files entirely:

    git rm ee/spec/factories/vulnerabilities/finding_pipelines.rb \
        ee/spec/models/vulnerabilities/finding_pipeline_spec.rb \
        ee/app/models/vulnerabilities/finding_pipeline.rb