Deprecate IS_RECORD_TABLE_WIDGET_ENABLED feature flag (#19662)

## Summary
- Removes the `IS_RECORD_TABLE_WIDGET_ENABLED` feature flag, making the
record table widget unconditionally available in dashboard widget type
selection
- The flag was already seeded as `true` for all new workspaces and only
gated UI visibility in one component
(`SidePanelPageLayoutDashboardWidgetTypeSelect`)
- Cleans up the flag from `FeatureFlagKey` enum, dev seeder, and test
mocks

## Analysis
The flag only controlled whether the "View" (Record Table) widget option
appeared in the dashboard widget type selector. The entire record table
widget infrastructure (rendering, creation hooks, GraphQL types,
`RECORD_TABLE` enum in `WidgetType`) is independent of the flag and
fully implemented. No backend logic depends on this flag.

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Charles Bochet <charles@twenty.com>

packages/twenty-server/src/engine/twenty-orm/entity-manager/workspace-entity-manager.spec.ts

@@ -242,7 +242,6 @@ describe('WorkspaceEntityManager', () => {
         IS_CONNECTED_ACCOUNT_MIGRATED: false,
         IS_RICH_TEXT_V1_MIGRATED: false,
         IS_RECORD_PAGE_LAYOUT_GLOBAL_EDITION_ENABLED: false,
-        IS_RECORD_TABLE_WIDGET_ENABLED: false,
         IS_DATASOURCE_MIGRATED: false,
         IS_COMMAND_MENU_ITEM_ENABLED: false,
       },