switch to win-x64 as per the suggested MS website

Author: loanstone

.github/workflows/dotnet.yml

@@ -19,7 +19,7 @@ jobs:
           - os: ubuntu-latest
             rid: linux-x64
           - os: windows-latest
-            rid: windows-x64
+            rid: win-x64
           - os: macos-latest
             rid: osx-x64