Move os out of matrix

as all tests run on ubuntu-latest anyway

Author: FloEdelmann

.github/workflows/CI.yml

@@ -27,15 +27,13 @@ jobs:
     strategy:
       matrix:
         node: [18, 20]
-        os: [ubuntu-latest]
         eslint: [8, 9]
         include:
           # On old Node version
-          - eslint: 8
-            node: 17
-            os: ubuntu-latest
+          - node: 17
+            eslint: 8
 
-    runs-on: ${{ matrix.os }}
+    runs-on: ubuntu-latest
     steps:
       - name: Checkout
         uses: actions/checkout@v3