maint: update code for Probot v13

Author: wolfy1339

app.js

@@ -2,7 +2,7 @@
  * @param {import('probot').Probot} app
  */
 module.exports = (app) => {
-  app.log("Yay! The app was loaded!");
+  app.log.info("Yay! The app was loaded!");
 
   app.on("issues.opened", async (context) => {
     return context.octokit.issues.createComment(