drop newly unused Application::ValidateSystemFont

Change-Id: Iffe850d99f2dcd9e955a4ba1190e010be905434b
don't screw around with the system font selection

Change-Id: I491a6410f70b063fd74834d5837be34e4b9552d7
Resolves: fdo#87281 Crash on importing diagram in .docx file

Change-Id: Ic2c7326ab83258e2e9dcbac88aa9f76f771a9b12