Add least-privilege permissions to CI workflow

Author: honnibal

.github/workflows/test.yml

@@ -2,6 +2,8 @@ name: Test
 
 on: [push, pull_request, workflow_call]
 
+permissions:
+  contents: read
 env:
   hf-transformers-pip: transformers[sentencepiece]>=3.4.0,<4.32.0