Appveyor - use cmake installed by default (3.20.2)

Version 3.11.4 doesn't support VS2019
It's possible this will still fail (issue #70)

Issue #96

Author: amaitland

appveyor.yml

@@ -7,10 +7,6 @@ shallow_clone: true
 # Start builds on tags only (GitHub and BitBucket)
 skip_non_tags: true
 
-#Cholatey install specific cmake
-install:
-  - cinst cmake.portable --version 3.11.4
-
 # to run your custom scripts instead of automatic MSBuild
 build_script:
   - ps: .\build.ps1