[INTERNAL][FIX] RenderManager writeIcon: Fix font-family quote handling
[INTERNAL][FIX] RenderManager writeIcon: Fix font-family quote handling

After latest API update the writeIcon method was rewritten and
quoting font names was unintentionally omitted.
It is now added back so RenderManager tests pass on Firefox.

Change-Id: Ie050b4614037b12a12aaf76a39e521a1cf3c6fa7
BCP: 1880733672

SAP/openui5,SAP/openui5,SAP/openui5,SAP/openui5