[Infra] Optimize release-prepare-pr workflow

This commit updates the `release-prepare-pr` GitHub Actions workflow to use `ubuntu-slim` instead of `ubuntu-latest`. This change aims to reduce resource consumption and potentially speed up job execution by using a more minimal runner environment.

Author: jacksever

.github/workflows/release-prepare-pr.yml

@@ -12,7 +12,7 @@ on:
 
 jobs:
   prepare-release:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-slim
     permissions:
       contents: write
       pull-requests: write