fix: upgrade payload from 1.9.2 to 1.15.8

Snyk has created this PR to upgrade payload from 1.9.2 to 1.15.8.

See this package in npm:
https://www.npmjs.com/package/payload

See this project in Snyk:
https://app.snyk.io/org/sammyfilly/project/7124466d-b886-4746-9916-f277cb489961?utm_source=github&utm_medium=referral&page=upgrade-pr

examples/cms-payload/package.json

@@ -21,7 +21,7 @@
     "dotenv": "^8.2.0",
     "express": "^4.17.1",
     "next": "latest",
-    "payload": "1.9.2",
+    "payload": "1.15.8",
     "payload-admin-bar": "^1.0.5",
     "pino-pretty": "^9.1.1",
     "react": "18.2.0",