Remove old relations (#11993)

This is a first PR to remove old relation logic

Next steps:
- remove relationMetadata from cache
- remove relationMetadata table content and structure
- refactor relationDefinition to leverage field.settings instead

packages/twenty-front/src/generated/graphql.tsx

@@ -587,7 +587,6 @@ export enum FeatureFlagKey {
   IsCopilotEnabled = 'IsCopilotEnabled',
   IsCustomDomainEnabled = 'IsCustomDomainEnabled',
   IsJsonFilterEnabled = 'IsJsonFilterEnabled',
-  IsNewRelationEnabled = 'IsNewRelationEnabled',
   IsPermissionsV2Enabled = 'IsPermissionsV2Enabled',
   IsPostgreSQLIntegrationEnabled = 'IsPostgreSQLIntegrationEnabled',
   IsStripeIntegrationEnabled = 'IsStripeIntegrationEnabled',