fix(setup_macos_executor): bump node v12 to v16

Author: mikehardy

src/commands/setup_macos_executor.yml

@@ -4,7 +4,7 @@ parameters:
   node_version:
     description: The version of Node to use. This can be either a major version ("8"), a major and minor ("8.4"), or a fully qualified version ("8.4.1").
     type: string
-    default: "12"
+    default: "16"
   homebrew_cache:
     description: Should we cache after brew install? Defaults to true
     type: boolean