(PUP-2881) Remove win32-taskscheduler gem + deps

 - win32-taskscheduler code has been partially vendored in Puppet core
   and rewritten to be FFI / x64 compatible.  This was done since the
   win32-taskscheduler 0.3.0 gem does not support Windows 2003, and
   Puppet needs to maintain backwards compatibility.
 - structured_warnings is only used by win32-taskscheduler and can be
   removed