Cleanup not needed build targets

Author: penguinolog

appveyor.yml

@@ -146,12 +146,6 @@ jobs:
         Python35_x86:
           python.version: '3.5'
           python.architecture: 'x86'
-        Python38_x64:
-          python.version: '3.8'
-          python.architecture: 'x64'
-        Python38_x86:
-          python.version: '3.8'
-          python.architecture: 'x86'
 
     steps:
       - task: UsePythonVersion@0