Change Homepage user preference based on feature flag

What does this MR do and why?

Related to #477090 (closed)

We are currently working on moving the Your work -> Projects page from HAML/vanilla JS to Vue. This will allow us to have UX parity across the product, implement filters more easily, and reduce technical debit. Part of this effort is changing the default tab from Yours to Contributed.

This means we need to update the Homepage user preference in /-/profile/preferences to reflect this new Contributed tab.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

your_work_projects_vue FF enabled	your_work_projects_vue FF disabled

How to set up and validate locally

1. Go to http://gdk.test:3000/rails/features and enable your_work_projects_vue feature flag
2. Go to http://gdk.test:3000/-/profile/preferences
3. The Homepage dropdown should show Your Contributed Projects (default)