normalizeStorePaths: strip version

Versions, like hashes, are volatile.

Avoids having to do things like https://github.com/nix-community/home-manager/pull/2816 indefinitely.

Regex crafted from https://github.com/NixOS/nix/blob/master/src/libstore/path.cc#L5-L17 and https://github.com/NixOS/nix/blob/master/src/libstore/names.cc#L22-L38