Add a missing `dropdownMenu: "main-button"` segmentation on new welcome page (#13294)

GitOrigin-RevId: 08e803f2ab2243d86b095cb5a7196c97cea5d276

services/web/frontend/js/features/project-list/components/welcome-message-new/welcome-message-create-new-project-dropdown.tsx

@@ -21,6 +21,7 @@ function WelcomeMessageCreateNewProjectDropdown({
   const handleClick = useCallback(() => {
     sendMB('welcome-page-create-first-project-click', {
       'welcome-page-redesign': 'enabled',
+      dropdownMenu: 'main-button',
       dropdownOpen: showDropdown,
     })