Update Go from 1.11 to 1.13.7

What does this MR do?

Updates Go from 1.11 to 1.13.7.

Template https://gitlab.com/gitlab-org/security-products/ci-templates/raw/master/includes-dev/analyzer.yml was already upgraded to Go 1.13 (golang:1.13.7).

What are the relevant issue numbers?

gitlab-org/security-products&2 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added
• [n/a] Documentation created/updated for GitLab EE, if necessary
• [n/a] Documentation created/updated for this project, if necessary
• [n/a] Documentation reviewed by technical writer or follow-up review issue created
• [n/a] Tests added for this feature/bug
• [n/a] Job definition updated, if necessary
  • [n/a] Auto-DevOps template
  • [n/a] Job definition example
  • [n/a] CI Templates
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer