support for notScopes in module

### Check for previous/existing GitHub issues

- [x] I have checked for previous/existing GitHub issues

### Issue Type?

Feature Request

### (Optional) Module Version

0.12.3

### (Optional) Correlation Id

_No response_

### Description

Despite mapping functionality being present in the main.policy_assignments.tf, there is no property in the map for policy_assignments_to_modify in variables.tf to support notScopes, meaning an override needs to be added into the library folder when deploying via the ALZ accelerator.

```tf
notScopes = optional(list(string), null)
```

Start in variables.tf and compare the policy_assignments_to_modify map with the existing notScopes mapping in main.policy_assignments.tf. Add the module input support for notScopes so deployments through the ALZ accelerator no longer need an override in the library folder. Done means the map accepts the optional list(string) property and the override is no longer required.

Written by the indexing model from the issue text.