Remove appveyor script; we can always re-enable if required.

appveyor.yml

@@ -1,32 +0,0 @@
-image: Visual Studio 2022
-
-shallow_clone: true
-
-
-environment:
-  matrix:
-    - Platform: x64
-    - Platform: Win32
-
-  Configuration: Release
-
-  SDL2_version: 2.24.0
-
-
-install:
-  - cmd: |
-      curl -o "C:\SDL2-devel.zip" "https://www.libsdl.org/release/SDL2-devel-%SDL2_version%-VC.zip"
-      7z x "C:\SDL2-devel.zip" -o"C:\"
-      xcopy /S "C:\SDL2-%SDL2_version%\include" src\common
-
-      if %Platform%==x64 xcopy /S "C:\SDL2-%SDL2_version%\lib\x64" src\os\windows
-      if %Platform%==Win32 xcopy /S "C:\SDL2-%SDL2_version%\lib\x86" src\os\windows
-
-
-build_script:
-  - cmd: |
-      msbuild src\os\windows\Stella.sln
-
-
-artifacts:
-  - path: '**\stella.exe'