fix(ci): use env context instead of secrets in step-level if condition (NVIDIA#452)

The secrets context is not available in step-level if expressions in
GitHub Actions — only in with and env blocks. This caused the workflow
file to be invalid, failing every run with:

  Unrecognized named-value: 'secrets'

Fix by exporting the secret to a job-level env var and checking that
in the step condition instead.

Co-authored-by: John Myers <johntmyers@users.noreply.github.com>

Author: johntmyers

.github/workflows/vouch-check.yml

@@ -12,10 +12,12 @@ jobs:
   vouch-gate:
     if: github.repository_owner == 'NVIDIA'
     runs-on: ubuntu-latest
+    env:
+      ORG_READ_TOKEN: ${{ secrets.ORG_READ_TOKEN }}
     steps:
       - name: Check org membership
         id: org-check
-        if: ${{ secrets.ORG_READ_TOKEN != '' }}
+        if: env.ORG_READ_TOKEN != ''
         uses: actions/github-script@v7
         with:
           github-token: ${{ secrets.ORG_READ_TOKEN }}