Remove book a call step from onboarding (#22597)

The book a call screen was shown as a dedicated onboarding step after
sending team invites. It is no longer part of the flow: the
`BOOK_ONBOARDING` status, its pending user var, the
`skipBookOnboardingStep` mutation and the `BookCallDecision` screen are
removed, and onboarding completes right after the plan step.

The `/book-call` Cal.com page remains, reachable only from the "Book a
Call" link on the upgrade screen, with a back link to `/plan-required`.

<!-- This is an auto-generated description by cubic. -->
<a
href="https://cubic.dev/pr/twentyhq/twenty/pull/22597?utm_source=github"
target="_blank" rel="noopener noreferrer"
data-no-image-dialog="true"><picture><source
media="(prefers-color-scheme: dark)"
srcset="https://www.cubic.dev/buttons/review-in-cubic-dark.svg"><source
media="(prefers-color-scheme: light)"
srcset="https://www.cubic.dev/buttons/review-in-cubic-light.svg"><img
alt="Review in cubic"
src="https://www.cubic.dev/buttons/review-in-cubic-dark.svg"></picture></a>
<!-- End of auto-generated description by cubic. -->

packages/twenty-front/src/modules/app/hooks/useCreateWorkspaceAppRouter.tsx

@@ -99,12 +99,6 @@ const PaymentSuccess = lazy(() =>
   })),
 );
 
-const BookCallDecision = lazy(() =>
-  import('~/pages/onboarding/BookCallDecision').then((module) => ({
-    default: module.BookCallDecision,
-  })),
-);
-
 const BookCall = lazy(() =>
   import('~/pages/onboarding/BookCall').then((module) => ({
     default: module.BookCall,
@@ -219,14 +213,6 @@ const createWorkspaceAppRouter = (
               </LazyRoute>
             }
           />
-          <Route
-            path={AppPath.BookCallDecision}
-            element={
-              <LazyRoute fallback={null}>
-                <BookCallDecision />
-              </LazyRoute>
-            }
-          />
           <Route
             path={AppPath.BookCall}
             element={