Update vulnerability_reads scanner in the ingestion pipeline

What does this MR do and why?

The bug fix is being backported as it was requested by a customer here and the fix is small and fairly low risk

As described in the original MR into the default branch, the scanner data can be inconsistent between the vulnerability_reads and vulnerability_occurrences tables for the same vulnerability.

This should never be the case, as they should always be referring to the same data. This is because vulnerability_reads is just a de-normalized read-optimized table containing heavily read data from the vulnerability and vulnerability_finding models

The scanner reference is being properly updated for the finding in the finding_map class.

This change makes it so that the existing vulnerability_reads is also updated with a new scanner reference

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• This MR is backporting a bug fix, documentation update, or spec fix, previously merged in the default branch.
  • merged in default here: !148016 (merged)
• The MR that fixed the bug on the default branch has been deployed to GitLab.com (not applicable for documentation or spec changes).
  • deployed to production Apr 1, 2024, 4:44 PM
• This MR has a severity label assigned (if applicable).
• Set the milestone of the merge request to match the target backport branch version.
• This MR has been approved by a maintainer (only one approval is required).
• Ensure the e2e:package-and-test-ee job has either succeeded or been approved by a Software Engineer in Test.

Note to the merge request author and maintainer

If you have questions about the patch release process, please:

• Refer to the patch release runbook for engineers and maintainers for guidance.
• Ask questions on the #releases Slack channel (internal only).