Remove feature flag for work in progress limits

What does this MR do?

Default to enabled: true for wip_limits and rely on gitlab starter license.

Repro Locally:

1. Remove Licesne
2. Go to issue boards list
3. Ensure you cannot see the gear icon

4. Add your license back in locally
5. Confirm you can see the gear icon above ☝
6. Extra Credit Turn FF off using `Feature.disable(:wip_limits) in the rails console and check the icon disappears as well.

Screenshots

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

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team