Remove the code of old show pages (#17811)

Closes https://github.com/twentyhq/core-team-issues/issues/2213

packages/twenty-server/src/engine/workspace-manager/dev-seeder/core/utils/seed-feature-flags.util.ts

@@ -36,11 +36,6 @@ export const seedFeatureFlags = async ({
         workspaceId: workspaceId,
         value: true,
       },
-      {
-        key: FeatureFlagKey.IS_RECORD_PAGE_LAYOUT_ENABLED,
-        workspaceId: workspaceId,
-        value: true,
-      },
       {
         key: FeatureFlagKey.IS_PUBLIC_DOMAIN_ENABLED,
         workspaceId: workspaceId,

packages/twenty-server/src/engine/workspace-manager/workspace-migration/constant/default-feature-flags.ts

@@ -4,5 +4,4 @@ export const DEFAULT_FEATURE_FLAGS = [
   FeatureFlagKey.IS_ATTACHMENT_MIGRATED,
   FeatureFlagKey.IS_NOTE_TARGET_MIGRATED,
   FeatureFlagKey.IS_TASK_TARGET_MIGRATED,
-  FeatureFlagKey.IS_RECORD_PAGE_LAYOUT_ENABLED,
 ] as const satisfies FeatureFlagKey[];