Use shallow clone (fetch-depth: 1) in ci-nightly.yml

Full history is not needed — we only read ci/versions.yml.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: leofang

.github/workflows/ci-nightly.yml

@@ -41,7 +41,7 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
         with:
-          fetch-depth: 0
+          fetch-depth: 1
 
       - name: Get CUDA build versions
         id: get-vars