Doxygen: Remove DOT_FONT* settings

Let Doxygen use the default, we don't really care.

doc/Doxyfile.in

@@ -1624,26 +1624,6 @@ HAVE_DOT               = YES
 
 DOT_NUM_THREADS        = 0
 
-# By default doxygen will use the Helvetica font for all dot files that
-# doxygen generates. When you want a differently looking font you can specify
-# the font name using DOT_FONTNAME. You need to make sure dot is able to find
-# the font, which can be done by putting it in a standard location or by setting
-# the DOTFONTPATH environment variable or by setting DOT_FONTPATH to the
-# directory containing the font.
-
-DOT_FONTNAME           = FreeSans.ttf
-
-# The DOT_FONTSIZE tag can be used to set the size of the font of dot graphs.
-# The default size is 10pt.
-
-DOT_FONTSIZE           = 10
-
-# By default doxygen will tell dot to use the Helvetica font.
-# If you specify a different font using DOT_FONTNAME you can use DOT_FONTPATH to
-# set the path where dot can find it.
-
-DOT_FONTPATH           =
-
 # If the CLASS_GRAPH and HAVE_DOT tags are set to YES then doxygen
 # will generate a graph for each documented class showing the direct and
 # indirect inheritance relations. Setting this tag to YES will force the