Auto-cancel PR CI when pushing to the same branch

This will reduce active runners on CI when making corrections, lowering costs
and hopefully increasing stability and wall times due to machine availability.

.github/workflows/pull-request.yml

@@ -5,6 +5,10 @@ on:
   merge_group:
     types: [checks_requested]
 
+concurrency:
+  group: ${{ github.workflow_ref }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   trigger-lint:
     name: Trigger linters