ci(buildkite): fix set auth token command

.buildkite/scripts/helpers/setup-registry.sh

@@ -2,10 +2,7 @@
 set -e
 
 echo "Authenticating against the GitHub package registry"
-# NOTE: we are adding a literal ${GITHUB_REGISTRY_TOKEN} to the npm config here;
-#       npm/pnpm will interpret it and sub in the environment variable for us,
-#       meaning we don't have to store the secret on disk.
-npm config set "//npm.pkg.github.com/:_authToken" '${GITHUB_REGISTRY_TOKEN}'
+npm config set '//npm.pkg.github.com/:_authToken' "${GITHUB_REGISTRY_TOKEN}"
 
 printf "Logged in as: "
 npm whoami --registry=https://npm.pkg.github.com