Update appveyor.yml

Checking if appveyor CI fails with just updating from VS 2017 to VS 2019.

Author: smoothdeveloper

appveyor.yml

@@ -1,12 +1,11 @@
 init:
   - git config --global core.autocrlf input
-image: Visual Studio 2017
+  - net start MSSQL$SQL2019
+image: Visual Studio 2019
 build_script:
   - cmd: build.cmd GenerateDocs
 test: off
 version: 0.0.1.{build}
 artifacts:
   - path: bin
     name: bin
-services:
-  - mssql2014