Do not color newline in log messages

What does this MR do?

Previously, we were colouring the newline (\n) character in log messages, but it caused gotestsum to fail. This MR fixes that issue by ensuring that we don't colour newline characters.

What are the relevant issue numbers?

Fix coloured log output in logutil package of s... (gitlab-org/gitlab#375625 - closed)

Testing

Tested in Update common to v3.2.1 to fix gotestsum cmd (report!45 - merged):

• go test job no longer shows any gotestsum failures

  $ gotestsum --junitfile report.xml --format testname -- -race -coverprofile=coverage.txt -covermode atomic ./...
  
  coverage: 83.1% of statements
  PASS . (coverage: 83.1% of statements)
  DONE 77 tests in 28.086s

• MR test widget in Update common to v3.2.1 to fix gotestsum cmd (report!45 - merged) no longer shows any failing tests:

  

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
  • 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