-Update CI

Author: thebigG

.github/workflows/windows_build.yaml

@@ -23,7 +23,7 @@ jobs:
       fail-fast: false
       matrix:
         config:
-          - { name: "ubuntu-18.04", os: "ubuntu-18.04" }
+          - { name: "ubuntu-20.04", os: "ubuntu-20.04" }
     steps:
       - name: Checkout
         uses: actions/checkout@v1