Avoids running duplicated workflows

.github/workflows/artifacts.yml

@@ -5,6 +5,10 @@ on:
     branches:
       - main
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   python_doc:
     runs-on: ubuntu-latest

.github/workflows/tests.yml

@@ -10,6 +10,10 @@ on:
   schedule:
     - cron: "0 0 * * 0"
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   fmt:
     runs-on: ubuntu-latest