Fix relative path of node_modules ignore.
Review Request #14204 — Created Oct. 15, 2024 and updated — Latest diff uploaded
A recent change made the node_modules directory in .gitignore relative
in order to surface bugs that can occur if there are extra node_modules
directories deeper in the tree, but this wasn't done with the correct
syntax so it ended up not matching the top-level node_modules directory
at all. This change fixes it.