User reported this issue when attempting to view PDFs.
See moderntribe/the-events-calendar@29a24e5 for work around.
Remove OTF fonts from being used
Mpdf only supports one type of OTF font file. From testing, it appears most fonts are the non-supported type. To prevent any confusion this change removes OTF fonts from being uploaded.
As a byproduct of this, issue #562 is fixed