fix: Revert "handle unpipeing, cancelling or destroying of busboy accordingly (#81)" (#108)

This reverts commit e41a643.

Author: Uzlopak

lib/types/multipart.js

@@ -174,15 +174,6 @@ function Multipart (boy, cfg) {
         ++nends
         const file = new FileStream(fileOpts)
         curFile = file
-        boy.on('unpipe', function () {
-          file.destroy()
-        })
-        boy.on('cancel', function () {
-          file.destroy()
-        })
-        boy.on('destroy', function () {
-          file.destroy()
-        })
         file.on('end', function () {
           --nends
           self._pause = false