Clean project helpers code after project sidebar refactor

What does this MR do?

After migrating the whole project sidebar to the new implementation, get can get rid of those methods that we no longer use.

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have not included a changelog entry because it's a tooling change.
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Separation of EE specific content