ci: limit concurrency of update and validate workflows (#75)

https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/control-the-concurrency-of-workflows-and-jobs

Author: joschi

.github/workflows/update.yml

@@ -6,6 +6,9 @@ on:
     - main
   schedule:
     - cron: '0 */6 * * *'
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
 jobs:
   update:
     runs-on: 'ubuntu-latest'

.github/workflows/validate.yml

@@ -3,6 +3,9 @@ on:
   workflow_dispatch:
   schedule:
     - cron: '0 3 * * *'
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
 jobs:
   validate:
     runs-on: 'ubuntu-latest'