Node.js: fixed ES modules format in loader.mjs.

Before Node.js v16.14.0 the "format" value in defaultResolve
was ignored so error was hidden.  For more information see:
https://github.com/nodejs/node/pull/40980

src/nodejs/unit-http/loader.mjs

@@ -4,13 +4,13 @@ export async function resolve(specifier, context, defaultResolver) {
         case "websocket":
             return {
                 url: new URL("./websocket.js", import.meta.url).href,
-                format: "cjs"
+                format: "commonjs"
             }
 
         case "http":
             return {
                 url: new URL("./http.js", import.meta.url).href,
-                format: "cjs"
+                format: "commonjs"
             }
     }