Remove unused logic from the bottom of the ZAP scripts

What does this MR do?

• Removes logic for config file generation, which is not supported by DAST
• Removes logic for printing the URL count, which is already handled by DAST
• Removes warning when no URLs are found, which was unreachable code because ZAP throws an IOError if it cannot reach the target URL
• Updates the Apache compliance comment to be more generic, to avoid having to write a long list of changes as we remove more code from the scripts

What are the relevant issue numbers?

gitlab-org/gitlab#218808 (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