Restored custom zap config file to fix slow scans

What does this MR do?

Ensures that DAST uses the custom DAST ZAP configuration file. This removes the tagging of requests which is known to be a performance impact on many scans.

What are the relevant issue numbers?

gitlab-org/gitlab#326786 (closed)

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 added for this feature/bug
• Job definition updated, if necessary
  • Job definition example
  • Vendored CI Templates (also in CE)
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer