Remove old vendored dropzone from serviceworker (#10703)

* Remove dropzone from serviceworker

* Remove CSS as well

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

templates/pwa/serviceworker_js.tmpl

@@ -12,7 +12,6 @@ var urlsToCache = [
   '{{StaticUrlPrefix}}/js/dropzone.js',
   '{{StaticUrlPrefix}}/vendor/plugins/codemirror/addon/mode/loadmode.js',
   '{{StaticUrlPrefix}}/vendor/plugins/codemirror/mode/meta.js',
-  '{{StaticUrlPrefix}}/vendor/plugins/dropzone/dropzone.js',
   '{{StaticUrlPrefix}}/vendor/plugins/emojify/emojify.custom.js',
   '{{StaticUrlPrefix}}/vendor/plugins/jquery.datetimepicker/jquery.datetimepicker.js',
   '{{StaticUrlPrefix}}/vendor/plugins/jquery.minicolors/jquery.minicolors.min.js',
@@ -25,7 +24,6 @@ var urlsToCache = [
   '{{StaticUrlPrefix}}/css/dropzone.css',
   '{{StaticUrlPrefix}}/fomantic/semantic.min.css?v={{MD5 AppVer}}',
   '{{StaticUrlPrefix}}/vendor/assets/font-awesome/css/font-awesome.min.css',
-  '{{StaticUrlPrefix}}/vendor/plugins/dropzone/dropzone.css',
   '{{StaticUrlPrefix}}/vendor/plugins/jquery.datetimepicker/jquery.datetimepicker.css',
   '{{StaticUrlPrefix}}/vendor/plugins/jquery.minicolors/jquery.minicolors.css',
   '{{StaticUrlPrefix}}/vendor/plugins/simplemde/simplemde.min.css',