doc: reset the default sphinx literal block format

Set the default literal block format for Sphinx docs
to 'none' instead of the implicit default of 'python'.

This means that default :: blocks won't have any
highlighting applied. Explicit highlighting via
the code-block:: directive is already available and
in use in the docs.

Signed-off-by: John McNamara <john.mcnamara@intel.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>

doc/guides/conf.py

@@ -38,6 +38,7 @@ from pygments.formatters.latex import LatexFormatter
 project = 'DPDK'
 
 html_show_copyright = False
+highlight_language = 'none'
 
 version = subprocess.check_output(['make', '-sRrC', '../../', 'showversion']).decode('utf-8')
 release = version