Update the commented out dependabot ignore directives

Add a directive for hashicorp/setup-packer that was missed when it was
added to the `build` workflow. Add a directive for
cisagov/setup-env-github-action that is not strictly necessary since we
currently just pull from the `develop` branch, but is good to have in
case we were to change that in the future.

.github/dependabot.yml

@@ -13,10 +13,12 @@ updates:
     #   - dependency-name: actions/checkout
     #   - dependency-name: actions/setup-go
     #   - dependency-name: actions/setup-python
+    #   - dependency-name: cisagov/setup-env-github-action
     #   - dependency-name: crazy-max/ghaction-dump-context
     #   - dependency-name: crazy-max/ghaction-github-labeler
     #   - dependency-name: crazy-max/ghaction-github-status
     #   - dependency-name: GitHubSecurityLab/actions-permissions
+    #   - dependency-name: hashicorp/setup-packer
     #   - dependency-name: hashicorp/setup-terraform
     #   - dependency-name: mxschmitt/action-tmate
     #   - dependency-name: step-security/harden-runner