Remove gitpod feature flag

What does this MR do?

It's time to remove this feature flag (see issue). Heads up! This feature is still configurable from the admin settings so it won't be available in a local instance until enabled in Admin > Settings > General > Gitpod

Screenshots (strongly suggested)

Project with settings enabled	User preferences with settings enabled	Project with settings disabled	User preferences with settings disabled

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

References

Related to #258206 (closed)