Updated AppVeyor so it only runs on PHP 7.2

Author: WyriHaximus

appveyor.yml

@@ -6,22 +6,10 @@ clone_folder: c:\projects\php-project-workspace
 ## Build matrix for lowest and highest possible targets
 environment:
   matrix:
-  - dependencies: lowest
-    php_ver_target: 7.0
-  - dependencies: lowest
-    php_ver_target: 7.1
   - dependencies: lowest
     php_ver_target: 7.2
-  - dependencies: current
-    php_ver_target: 7.0
-  - dependencies: current
-    php_ver_target: 7.1
   - dependencies: current
     php_ver_target: 7.2
-  - dependencies: highest
-    php_ver_target: 7.0
-  - dependencies: highest
-    php_ver_target: 7.1
   - dependencies: highest
     php_ver_target: 7.2