Update dependency @octokit/app to v15

Author: renovate[bot]

package.json

@@ -17,7 +17,7 @@
     "fix": "run-s fix:prettier fix:eslint"
   },
   "dependencies": {
-    "@octokit/app": "14.1.0",
+    "@octokit/app": "15.0.1",
     "@octokit/graphql-schema": "15.18.0",
     "@prantlf/jsonlint": "14.0.3",
     "dotenv": "16.4.5",