Remove schema V14 support

What does this MR do?

Now that schema V15 is the only accepted version on GitLab (since 16.0), we can drop any V14 related code.

• default to V15 and drop V14 overrides
• update fixtures to schema V15
• remove V14 properties that are no longer used in V15
• fix cve display on the table log output

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog trailer 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
  • Auto-DevOps template
  • Job definition example
  • CI Templates
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer