fix(payments-next): Fix offer page

Because:

* Reason was not optional

This commit:

*

Author: elizabeth-ilina

libs/payments/ui/src/lib/nestapp/validators/GetInterstitialOfferContentActionResult.ts

@@ -44,8 +44,9 @@ export class GetInterstitialOfferContentActionResult {
   @Type(() => PageContent)
   pageContent!: PageContent | null;
 
+  @IsOptional()
   @IsString()
-  reason!: string;
+  reason?: string;
 
   @IsOptional()
   @IsString()