switch to polka, remove unused deps

test/app/routes/api/delete/[id].js

@@ -1,5 +1,5 @@
 export function del(req, res) {
-	res.set({
+	res.writeHead(200, {
 		'Content-Type': 'application/json'
 	});
 

test/app/routes/blog.json.js

@@ -8,7 +8,7 @@ const contents = JSON.stringify(posts.map(post => {
 }));
 
 export function get(req, res) {
-	res.set({
+	res.writeHead(200, {
 		'Content-Type': 'application/json',
 		'Cache-Control': `max-age=${30 * 60 * 1e3}` // cache for 30 minutes
 	});

test/app/routes/blog/[slug].json.js

@@ -11,7 +11,7 @@ export function get(req, res, next) {
 	const { slug } = req.params;
 
 	if (slug in lookup) {
-		res.set({
+		res.writeHead(200, {
 			'Content-Type': 'application/json',
 			'Cache-Control': `no-cache`
 		});