Switch to workflow_call for GitHub Actions CI

.github/workflows/ci.yaml

@@ -1,3 +1,4 @@
+---
 name: Run tests
 
 on:
@@ -6,26 +7,5 @@ on:
   pull_request:
 
 jobs:
-  setup:
-    runs-on: ubuntu-latest
-    outputs:
-      strategy: ${{steps.load.outputs.strategy}}
-
-    steps:
-      - uses: actions/checkout@v2
-        with:
-          repository: colcon/ci
-      - id: load
-        run: echo "::set-output name=strategy::$(echo $(cat strategy.json))"
-
   pytest:
-    needs: [setup]
-    strategy: ${{fromJson(needs.setup.outputs.strategy)}}
-    runs-on: ${{matrix.os}}
-
-    steps:
-      - uses: actions/checkout@v2
-      - uses: actions/setup-python@v2
-        with:
-          python-version: ${{matrix.python}}
-      - uses: colcon/ci@v1
+    uses: colcon/ci/.github/workflows/pytest.yaml@main