Change the name of the generated pdf.sandbox.external for mozilla-central
Change the name of the generated pdf.sandbox.external for mozilla-central

This patch is blocking https://phabricator.services.mozilla.com/D148600.

mozilla/pdf.js,Shoobx/pdf.js,nawawi/pdf.js,Shoobx/pdf.js,Snuffleupagus/pdf.js,Snuffleupagus/pdf.js,timvandermeij/pdf.js,showpad/mozilla-pdf.js,Snuffleupagus/pdf.js,mozilla/pdf.js,showpad/mozilla-pdf.js,timvandermeij/pdf.js,nawawi/pdf.js,Shoobx/pdf.js,timvandermeij/pdf.js,showpad/mozilla-pdf.js,nawawi/pdf.js,mozilla/pdf.js