Stop job cancelling

Author: mpickering

.github/workflows/validate.yml

@@ -6,11 +6,6 @@ defaults:
   run:
     shell: bash
 
-# See: https://docs.github.com/en/actions/reference/workflow-syntax-for-github-actions#concurrency.
-concurrency:
-  group: ${{ github.ref }}-${{ github.workflow }}
-  cancel-in-progress: true
-
 on:
   push:
     branches: