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-client-sdk/src/metadata/generated/schema.graphql

@@ -995,7 +995,6 @@ enum OnboardingStatus {
   SYNC_EMAIL
   APPS_INSTALLATION
   INVITE_TEAM
-  BOOK_ONBOARDING
   COMPLETED
 }
 
@@ -3344,7 +3343,6 @@ type Mutation {
   revokeApiKey(input: RevokeApiKeyInput!): ApiKey
   assignRoleToApiKey(apiKeyId: UUID!, roleId: UUID!): Boolean!
   skipSyncEmailOnboardingStep: OnboardingStepSuccess!
-  skipBookOnboardingStep: OnboardingStepSuccess!
   triggerInstallAppsOnboardingStep(universalIdentifiers: [String!]!): OnboardingStepSuccess!
   updateOneApplicationVariable(key: String!, value: String!, applicationId: UUID!): Boolean!
   checkoutSession(recurringInterval: SubscriptionInterval!, plan: BillingPlanKey! = PRO, requirePaymentMethod: Boolean! = true, successUrlPath: String): BillingSession!