specify workflow permissions; remove concurrency

Author: lcian

.github/workflows/ci-python.yml

@@ -1,15 +1,14 @@
 name: CI / Python
 
+permissions:
+  contents: read
+
 on:
   push:
     branches:
       - main
   pull_request:
 
-concurrency:
-  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
-  cancel-in-progress: true
-
 jobs:
   lint:
     name: Lint