chore(cognito-identitypool-alpha): remove unused awslint condition (a…

…ws#33550)

### Issue # (if applicable)

N/A

### Reason for this change

A previous PR removed the `IdentityPoolRoleAttachmentProps` interface, so the linting exclusion is not necessary anymore.

### Description of changes

Removed unused linting exclusion from `aws-cognito-identitypool-alpha/awslint.json`.

### Describe any new or updated permissions being added

N/A

### Description of how you validated changes

`yarn build && yarn test`

### 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)

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

packages/@aws-cdk/aws-cognito-identitypool-alpha/awslint.json

@@ -1,5 +1 @@
-{
-  "exclude": [
-    "props-physical-name:@aws-cdk/aws-cognito-identitypool-alpha.IdentityPoolRoleAttachmentProps"
-  ]
-}
+{}