Fix a typo in firefox print service (bug 1777693)
Fix a typo in firefox print service (bug 1777693)

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