spark-wallet: switch from nodejs 10 to 12

nixpkgs starts marking nodejs 10 as insecure because it is end of life.

pkgs/spark-wallet/composition.nix

@@ -2,7 +2,7 @@
 
 {pkgs ? import <nixpkgs> {
     inherit system;
-  }, system ? builtins.currentSystem, nodejs ? pkgs."nodejs-10_x"}:
+  }, system ? builtins.currentSystem, nodejs ? pkgs."nodejs-12_x"}:
 
 let
   nodeEnv = import "${toString pkgs.path}/pkgs/development/node-packages/node-env.nix" {

pkgs/spark-wallet/generate.sh

@@ -29,7 +29,7 @@ jq '.dependencies["qrcode-terminal"] = .optionalDependencies["qrcode-terminal"]'
 
 # Generate nix pkg
 node2nix \
-  --nodejs-10 \
+  --nodejs-12 \
   --input $src/package.json \
   --lock $src/npm-shrinkwrap.json \
   --composition composition.nix \