Remove vueify_shared_runners_toggle feature flag [RUN ALL RSPEC] [RUN AS-IF-FOSS]

What does this MR do?

See #292441 (closed)

Remove vueify_shared_runners_toggle feature flag

The feature flag vueify_shared_runners_toggle has been rolled out successfully so this change removes it from the codebase as if set to true.

Changelog: changed

Screenshots (strongly suggested)

Please refer to #292441 (closed)

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because this feature flag is already enabled by default.
• [-] 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