chore: add assertions to integ tests using AwsCustomResource (#29929)

Closes #29937 

### Reason for this change

Adding assertions for `AwsCustomResource` will improve our test coverage.

### Description of changes

Added assertions for `AwsCustomResource` to integ tests that were impacted by this [PR](#29868).

### Description of how you validated changes

Assertions were validated by running the integ tests and verifying that it succeeded.

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk-testing/framework-integ/test/aws-elasticloadbalancingv2-actions/test/integ.cognito.js.snapshot/integ-cognito.template.json

@@ -918,6 +918,14 @@
    "Export": {
     "Name": "integ-cognito:ExportsOutputRefSignin352C80E64BA58F71"
    }
+  },
+  "ExportsOutputRefUserPool6BA7E5F296FD7236": {
+   "Value": {
+    "Ref": "UserPool6BA7E5F2"
+   },
+   "Export": {
+    "Name": "integ-cognito:ExportsOutputRefUserPool6BA7E5F296FD7236"
+   }
   }
  },
  "Parameters": {