UpdateSubscriptionJob should not be enqueued if billing is not enabled (#5007)

## Context
Adding this check to avoid enqueuing this job and following return-early
good practice

## Test
Without IS_BILLING_ENABLED env set

<img width="565" alt="Screenshot 2024-04-17 at 15 31 12"
src="https://github.com/twentyhq/twenty/assets/1834158/fcc43ce0-4455-4c4a-9889-02d99f0cd519">

With IS_BILLING_ENABLED env set
<img width="581" alt="Screenshot 2024-04-17 at 15 32 28"
src="https://github.com/twentyhq/twenty/assets/1834158/dc9756bd-2f6b-49bd-8897-84b6d8e09d56">

packages/twenty-server/src/engine/core-modules/billing/listeners/billing-workspace-member.listener.ts

@@ -9,12 +9,14 @@ import {
   UpdateSubscriptionJob,
   UpdateSubscriptionJobData,
 } from 'src/engine/core-modules/billing/jobs/update-subscription.job';
+import { EnvironmentService } from 'src/engine/integrations/environment/environment.service';
 
 @Injectable()
 export class BillingWorkspaceMemberListener {
   constructor(
     @Inject(MessageQueue.billingQueue)
     private readonly messageQueueService: MessageQueueService,
+    private readonly environmentService: EnvironmentService,
   ) {}
 
   @OnEvent('workspaceMember.created')
@@ -22,6 +24,10 @@ export class BillingWorkspaceMemberListener {
   async handleCreateOrDeleteEvent(
     payload: ObjectRecordCreateEvent<WorkspaceMemberObjectMetadata>,
   ) {
+    if (!this.environmentService.get('IS_BILLING_ENABLED')) {
+      return;
+    }
+
     await this.messageQueueService.add<UpdateSubscriptionJobData>(
       UpdateSubscriptionJob.name,
       { workspaceId: payload.workspaceId },