[Remove legacy waffle flags] Remove Legacy UI Waffle Flag Consumers — Phase 1a

[farhan]

Part of #521 — Remove Legacy Studio UI Waffle Flags
Frontend ticket: openedx/frontend-app-authoring#3063

/cc @openedx/axim-aximprovements

Scope

Remove routing flag consumers from the four simplest files in `frontend-app-authoring`. Each is a single-flag ternary change.

Tasks

1. `src/textbooks/hooks.jsx`

• 1 flag (`useNewCourseOutlinePage`), 1 ternary in the `breadcrumbs` array — hardcode to `/course/${courseId}`
• `waffleFlags` is a function parameter; remove it from the signature and update the caller

2. `src/custom-pages/CustomPages.tsx`

• 1 flag (`useNewCourseOutlinePage`), 1 ternary in the breadcrumb `to` value — hardcode to `/course/${courseId}`
• Remove `useWaffleFlags` call (line 73) and its import if no other flags are consumed

3. `src/studio-home/card-item/index.tsx`

• 1 flag (`useNewCourseOutlinePage`) in one boolean condition (line 255) — hardcode to `true` / remove guard
• Remove `useWaffleFlags` call and import if no other flags remain

4. `src/course-checklist/ChecklistSection/ChecklistItemComment.jsx`

• 1 flag (`useNewCourseOutlinePage`) in `getPathToCourseOutlinePage` helper — hardcode to the new path
• Remove `useWaffleFlags` call and `getConfig` import if no longer needed

Acceptance Criteria

• No references to the removed flag names remain in these 4 files
• `make validate.ci` passes