Update to Node 20 in docker-compose.yml

Node version 14 is quite out of date, but most notably there is a 60
second penalty imposed by NodeSource as a way of warning users to
upgrade.

Co-authored-by: An Stewart <andrew@super.gd>

docker-compose.yml

@@ -24,7 +24,7 @@ services:
       args:
         RUBY_VERSION: "3.1"
         PG_VERSION: 13
-        NODE_VERSION: 14
+        NODE_VERSION: 20
         MYSQL_VERSION: "8.0"
         BUNDLER_VERSION: 2
     image: solidus-4.4.0.dev