fix(deps): bump @octokit/webhooks in order to fix web users (#594)

The `verifyWithFallback()` function was missing from the web code, and was only defined for Node, leaving users unable to use newer versions of `@octokit/webhooks` with this package

Author: wolfy1339

package-lock.json

@@ -26,7 +26,7 @@
     "@octokit/oauth-app": "^7.1.5",
     "@octokit/plugin-paginate-rest": "^11.3.6",
     "@octokit/types": "^13.6.2",
-    "@octokit/webhooks": "^13.4.2"
+    "@octokit/webhooks": "^13.5.1"
   },
   "devDependencies": {
     "@octokit/tsconfig": "^4.0.0",