Removing override for credentials node version

[matthugs]

this is a bit of a "kick the bucket" change, but I anticipate we should not override the node version without overriding the npm version as well. Those versions not matching appears to cause node-sass to be installed improperly, or for npm to not be installed in an in-Docker usable way at all.

But either way this was prompted by the fact that this situation had broken make dev.static.credentials in edx/devstack.

Configuration Pull Request