appveyor: Change image to Visual Studio 2017

appveyor's Visual Studio 2022 images update on September 4, 2024
removed support for python 3.7 as documented in https://www.appveyor.com/updates/2024/06/13/.

Author: loqs

.appveyor.yml

@@ -1,7 +1,8 @@
 # appveyor.yml - https://www.appveyor.com/docs/lang/python
-# https://www.appveyor.com/docs/windows-images-software/#visual-studio-2022
+# https://www.appveyor.com/docs/windows-images-software/#visual-studio-2017
 ---
-image: Visual Studio 2022
+image: Visual Studio 2017
+
 environment:
   matrix:
     - PY_PYTHON: 2.7