Fix env var in conformance.yml

Author: sjberman

.github/workflows/conformance.yml

@@ -137,7 +137,7 @@ jobs:
 
       - name: Setup license file for plus
         if: ${{ inputs.image == 'plus' }}
-        run: echo "$PLUS_LICENSE" > license.jwt
+        run: echo "${PLUS_LICENSE}" > license.jwt
         env:
           PLUS_LICENSE: ${{ secrets.JWT_PLUS_REGISTRY }}