Don't pin SDK version, this just tends to mean we're running an outdated one

Author: nblumhardt

appveyor.yml

@@ -2,10 +2,8 @@ version: '{build}'
 skip_tags: true
 image: Visual Studio 2022
 configuration: Release
-install:
-  - ps: ./Setup.ps1
 build_script:
-- ps: ./Build.ps1
+- pwsh: ./Build.ps1
 test: false
 artifacts:
 - path: artifacts/Serilog.*.nupkg