take os out of the matrix again

Author: svlandeg

.github/workflows/test.yml

@@ -23,6 +23,7 @@ env:
 
 jobs:
   test:
+    runs-on: ubuntu-latest
     strategy:
       matrix:
         python-version:
@@ -31,12 +32,10 @@ jobs:
           - "3.10"
           - "3.11"
           - "3.12"
-        os: ubuntu-latest
         pydantic-version:
           - pydantic-v1
           - pydantic-v2
       fail-fast: false
-    runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v4
       - name: Set up Python