PLT-1388: Add Sandbox Environment Back to Deploy Matrix for github-actions-role (#329)

## 🎫 Ticket

https://jira.cms.gov/browse/PLT-1388

## 🛠 Changes

Adds sandbox back to the deploy matrix for `github-actions-role`.

## ℹ️ Context

We had a code freeze on the sandbox environment for the pentesting that
ended 10/10/2025. This PR aims to add the sandbox environment back to
the deploy matrix to reflect changes that were made to the permissions
of the `github-actions-role`, bringing it into parity with the other
environments.

## 🧪 Validation
This change has been validated in
#321

Author: gfreeman-navapbc

.github/workflows/tf-github-actions-role.yml

@@ -40,7 +40,7 @@ jobs:
       fail-fast: false
       matrix:
         app: [ab2d, bcda, dpc]
-        env: [dev, test, prod] # TODO Add sandbox env back in after pentest ends on 2025-10-10
+        env: [dev, test,sandbox, prod]
         include:
           - app: cdap
             env: mgmt