appveyor: never save cache after a failed CI run

.appveyor.yml

@@ -180,11 +180,6 @@ before_build:
 build_script:
   - python tools\build.py
 
-after_build:
-  # The build completed successfully; make sure the cache gets saved even if
-  # some tests fail.
-  - ps: $env:APPVEYOR_SAVE_CACHE_ON_ERROR = "true"
-
 test_script:
   - python tools\lint.py
   - ps: Exec { & python tools\test.py $env:DENO_BUILD_PATH }