Auto merge of rust-lang#3908 - RalfJung:perms, r=RalfJung

looks like we need more permissions

The cron job [failed](https://github.com/rust-lang/miri/actions/runs/11007186322/job/30563264024) last night, so let's see if this helps.

Author: bors

src/tools/miri/.github/workflows/ci.yml

@@ -13,7 +13,9 @@ on:
     - cron: '44 4 * * *' # At 4:44 UTC every day.
 
 permissions:
-  contents: read
+  # The cronjob needs to be able to push to the repo...
+  contents: write
+  # ... and create a PR.
   pull-requests: write
 
 defaults: