Correcting error mesasge.

src/Core/AdminConsole/Services/Implementations/PolicyService.cs

@@ -289,7 +289,7 @@ private async Task HasVerifiedDomainsAsync(Organization org)
         if (_featureService.IsEnabled(FeatureFlagKeys.AccountDeprovisioning)
             && await _organizationHasVerifiedDomainsQuery.HasVerifiedDomainsAsync(org.Id))
         {
-            throw new BadRequestException("Organization has verified domains.");
+            throw new BadRequestException("The Single organization policy is required for organizations that have enabled domain verification.");
         }
     }