python3-pycparser: cleanup RDEPENDS

- Drop python3-pprint, the source code no longer imports this module
- Drop python3-ply, ply package is bunled into pycparser, making the external python3-ply
dependency not useful. This seems to have been changed a long time ago in version 2.09 (2012.12.27)

Note about python3-netclient: It can be removed at a later date. There is one 'unused' import
for base64 in the ply source. Once that is cleaned up, python3-netclient can be removed.

Signed-off-by: Guðni Már Gilbert <gudnimar@noxmedical.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>