Clean up glTooltips feature flag [RUN ALL RSPEC] [RUN AS-IF-FOSS]

What does this MR do?

This Merge Request cleans the feature flag related code that allows us to have two tooltip implementations living alongside in GitLab. This is final piece of the puzzle to remove Bootstrap/jQuery tooltips from GitLab and replace them with GitLab UI tooltips.

Please, see for more information &4383 (closed)

Screenshots (strongly suggested)

This Merge Request does not introduce user-facing changes

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
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

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

Related to #292972 (closed)