Clarify comments in workflow.

Author: jaredhanson

.github/workflows/node.js.yml

@@ -83,8 +83,8 @@ jobs:
     - run: npm ci
       # The [`ci`][1] command was [introduced][2] with npm@5, and is intended to
       # be used in continuous integration environments.  If npm@5 or later is
-      # installed, `npm ci` is executed to install dependencies.  Otherwise,
-      # `npm install` is executed.
+      # installed and the package-lock.json file exists, `npm ci` is executed to
+      # install dependencies.  Otherwise, `npm install` is executed.
       #
       # [1]: https://docs.npmjs.com/cli/v10/commands/npm-ci
       # [2]: https://blog.npmjs.org/post/171556855892/introducing-npm-ci-for-faster-more-reliable