maybe windows-latest will work now

Author: nimrof

.github/workflows/dotnet.yml

@@ -9,8 +9,7 @@ on:
 jobs:
   build:
 
-    runs-on: windows-2019
-#    runs-on: windows-latest # error MSB3644: The reference assemblies for .NETFramework,Version=v4.5 were not found.
+    runs-on: windows-latest
 #    runs-on: ubuntu-latest # Error: setup-msbuild can only be run on Windows runners
     steps:
     - name: Checkout