Fix gitignore mistake (#6431)
Fix gitignore mistake (#6431)

Attempt to ignore all node_modules in concrete-stroage.
PolymerLabs/arcs,PolymerLabs/arcs,PolymerLabs/arcs,PolymerLabs/arcs,PolymerLabs/arcs,PolymerLabs/arcs,PolymerLabs/arcs,PolymerLabs/arcs