Update `Homepage` user preference options

Background

After completing all the issues in &13066 the tabs will have slightly different names. The first tab will be Contributed. We need to update the options in the Homepage user preference to reflect this name change.

Proposal

Change Your projects (default) to Your contributed projects (default). This change should be behind the your_work_projects_vue feature flag

Implementation guide

1. Check your_work_projects_vue feature flag and change string at app/helpers/preferences_helper.rb#L31