Revert "Add "unset-current-credentials: true" to CI/CD"

This reverts commit aed7091.

The pipeline still fails after setting the OIDC "permissions" block from
commit 025fbcd:

- https://github.com/mbland/elistman/actions/runs/6150360194/job/16688176092

Now I'm wondering if the "unset-current-credentials" setting is
interfering with it. Let's see.

.github/workflows/pipeline.yaml

@@ -135,7 +135,6 @@ jobs:
           role-session-name: testing-packaging
           role-duration-seconds: 3600
           role-skip-session-tagging: true
-          unset-current-credentials: true
 
       - name: Validate SAM template
         run: |