doc: removed Apex Sans font, replace with font from GFE

Signed-off-by: Ross Turk <rturk@redhat.com>
doc: alter doc CSS for the removal of Apex Sans

Signed-off-by: Ross Turk <rturk@redhat.com>
Merge pull request #1887 from rossturk/wip-rturkfonts

doc: remove Apex Sans from generated doc HTML