fix matrix setup for OS

Author: petems

.github/workflows/acceptance.yml

@@ -5,7 +5,7 @@ jobs:
     strategy:
       matrix:
         os: ["ubuntu:latest", "debian:latest", "fedora:latest", "centos:7"]
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
     steps:
     - name: Checkout code
       uses: actions/checkout@v2