Use native fetch

lib/request.js

@@ -1,6 +1,6 @@
 import core from "@actions/core";
 import { request } from "@octokit/request";
-import { EnvHttpProxyAgent, fetch as undiciFetch } from "undici";
+import { EnvHttpProxyAgent } from "undici";
 
 const baseUrl = core.getInput("github-api-url").replace(/\/$/, "");
 
@@ -12,7 +12,6 @@ export default request.defaults({
   },
   baseUrl,
   request: {
-    fetch: undiciFetch,
-    dispatcher: envHttpProxyAgent
+    dispatcher: envHttpProxyAgent,
   },
 });