Simplify the disabling of Node polyfills, in `gulpfile.js`, since we're now using Webpack 3.x
Simplify the disabling of Node polyfills, in `gulpfile.js`, since we're now using Webpack 3.x

Webpack was updated a while back, but we apparently forgot to update `gulpfile.js` as well.

macroplant/pdf.js,xavier114fch/pdf.js,adlerweb/pdf.js-Touch,timvandermeij/pdf.js,macroplant/pdf.js,Snuffleupagus/pdf.js,timvandermeij/pdf.js,Rob--W/pdf.js,websirnik/pdf.js,mozilla/pdf.js,showpad/mozilla-pdf.js,showpad/mozilla-pdf.js,macroplant/pdf.js,nawawi/pdf.js,mainegreen/pdf.js,websirnik/pdf.js,mukulmishra18/pdf.js,nawawi/pdf.js,Shoobx/pdf.js,xavier114fch/pdf.js,mozilla/pdf.js,caremerge/pdf.js,Snuffleupagus/pdf.js,Rob--W/pdf.js,Shoobx/pdf.js,Shoobx/pdf.js,mainegreen/pdf.js,showpad/mozilla-pdf.js,mukulmishra18/pdf.js,mozilla/pdf.js,Snuffleupagus/pdf.js,caremerge/pdf.js,timvandermeij/pdf.js,adlerweb/pdf.js-Touch,nawawi/pdf.js