Fix assert unreachable, remove unused variables (#13753)

Small code cleanup

packages/twenty-server/src/engine/core-modules/billing/commands/billing-sync-plans-data.command.ts

@@ -137,7 +137,7 @@ export class BillingSyncPlansDataCommand extends MigrationCommandRunner {
   }
 
   override async runMigrationCommand(
-    passedParams: string[],
+    _passedParams: string[],
     options: MigrationCommandOptions,
   ): Promise<void> {
     const billingMeters = await this.stripeBillingMeterService.getAllMeters();

packages/twenty-server/src/engine/core-modules/billing/stripe/stripe-sdk/mocks/stripe-sdk.mock.ts

@@ -3,7 +3,7 @@
 import type Stripe from 'stripe';
 
 export class StripeSDKMock {
-  constructor(private readonly apiKey: string) {}
+  constructor(private readonly _apiKey: string) {}
 
   customers = {
     update: (_id: string, _params?: Stripe.CustomerUpdateParams) => {