vdrsymbols: change license to bitstreamVera and publicDomain

pkgs/data/fonts/vdrsymbols/default.nix

···
     # Copyright (c) 2006 by Tavmjong Bah. All Rights Reserved.
     # DejaVu changes are in public domain
     # See https://dejavu-fonts.github.io/License.html for details
-    license = licenses.free;
+    license = with licenses; [ bitstreamVera publicDomain ];
   };
 }