Cleanup appveyor script (#117).
Cleanup appveyor script (#117).

Net-net: stick to grabbing the latest.

Fixes: https://github.com/dart-lang/linter/issues/117

BUG=
R=devoncarew@google.com

Review URL: https://codereview.chromium.org//2012803002 .

dart-lang/linter,alexeieleusis/dart-lang_linter,alexeieleusis/dart-lang_linter,dart-lang/linter