fix(utopia-remix) Add an endpoint for proxying PR branch deletion

utopia-remix/app/routes/internal.branch.tsx

@@ -0,0 +1,9 @@
+import { ActionFunctionArgs } from '@remix-run/node'
+import { handle } from '../util/api.server'
+import { proxy } from '../util/proxy.server'
+
+export async function action(args: ActionFunctionArgs) {
+  return handle(args, {
+    DELETE: proxy,
+  })
+}