Don't try to cache the src\packages folder in the appveyor build.

The folder is no longer used and caused a warning during the build.

Author: kll

appveyor.yml

@@ -13,6 +13,3 @@ build_script:
 
 test: off
 skip_tags: true
-
-cache:
-  - src\packages -> **\packages.config  # preserve "packages" directory in the root of build folder but will reset it if packages.config is modified