Bump Node.js to v18 per Pending v16 EOL (#1314)

Node.js 16.x will leave maintenance status 2022-09-11. Source: https://github.com/nodejs/release#release-schedule.

Per the OpenJS foundation, the 18.x series is currently recommended. Source: https://nodejs.org/en.

Resolves #1313

default.nix

@@ -1 +1 @@
-with import <nixpkgs> {}; stdenv.mkDerivation { name = "malloy"; buildInputs = [ nodejs-16_x jdk8 google-cloud-sdk postgresql git cacert openssh jq fakeroot]; }
+with import <nixpkgs> {}; stdenv.mkDerivation { name = "malloy"; buildInputs = [ nodejs-18_x jdk8 google-cloud-sdk postgresql git cacert openssh jq fakeroot]; }