[Backport 9.2] Stop passing token to validate-pr

[github-actions]

Backport b98fd2d from #5453.

[github-actions]

Following you can find the validation changes against the target branch for the APIs.

API	Status	Request	Response
bulk	🟢	536/536 → 537/537	554/554 → 555/555
index	🟢	1435/1435 → 1437/1437	1437/1437 → 1439/1439
indices.create	🔴	1351/1377 → 1355/1382	1377/1377 → 1382/1382
indices.flush	🟢	52/52 → 54/54	52/52 → 54/54
indices.get_mapping	🔴	197/197 → 199/199	188/197 → 188/199
indices.get_settings	🔴	85/85 → 86/86	66/85 → 66/86
indices.put_mapping	🟢 → 🔴	145/145 → 146/147	148/148 → 150/150
indices.refresh	🟢	327/327 → 328/328	327/327 → 328/328
search	🔴	2569/2608 → 2572/2611	2608/2608 → 2611/2611

You can validate these APIs yourself by using the make validate target.