docs(maintainers): remove jwerner from Rockchip

I originally added myself here because I had experience with the rk3399
code, when there were no other maintainers and that was the only
supported Rockchip SoC. Nowadays there are maintainers from the actual
manufacturer and most changes concern other SoCs, so I don't think it
makes sense for me to still be on here.

Change-Id: Id75089e62cf1a8b4cf1a27903808922968520636
Signed-off-by: Julius Werner <jwerner@chromium.org>

docs/about/maintainers.rst

@@ -858,8 +858,6 @@ RockChip platform port
 :|G|: `rockchip-linux`_
 :|M|: Heiko Stuebner <heiko@sntech.de>
 :|G|: `mmind`_
-:|M|: Julius Werner <jwerner@chromium.org>
-:|G|: `jwerner-chromium`_
 :|F|: plat/rockchip/
 
 STMicroelectronics platform ports