Bump to OpenWrt 19.07.3

Signed-off-by: Roger Pueyo Centelles <roger.pueyo@guifi.net>

options.conf.local

 release=Neumann
 version=testing
-openwrt_release=19.07.2
+openwrt_release=19.07.3
 base_url=https://downloads.openwrt.org/releases/$openwrt_release/targets/
 communities_git=https://github.com/libremesh/network-profiles.git
 communities_dir=communities

qmp.feeds.conf

-src-git base https://github.com/openwrt/openwrt.git;v19.07.2
+src-git base https://github.com/openwrt/openwrt.git;v19.07.3
 src-git packages https://github.com/openwrt/packages.git;openwrt-19.07
 src-git luci https://github.com/openwrt/luci.git;openwrt-19.07
 src-git routing https://github.com/openwrt-routing/packages.git;openwrt-19.07