Drop Mac OS (Buildalyzer#307)

Author: Corniel

.github/workflows/build.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [windows-latest, ubuntu-latest, macos-13]
+        os: [windows-latest, ubuntu-latest]
     env:
       # https://github.com/NuGet/Home/issues/11548
       # https://twitter.com/xoofx/status/1488617114940452872?s=20&t=BKSN4j9rP6fOyg8l7aW0eg
@@ -27,6 +27,7 @@ jobs:
           dotnet-version: |
             3.1.x
             8.0.x
+            9.0.x
       - name: Build and Test
         run: dotnet test --logger "trx;LogFileName=test-results.trx"
       - name: Upload Test Results