gluon-core: remove deprecated accept_ra settings

package/gluon-core/files/lib/gluon/upgrade/core/initial/011-gluon-network

@@ -10,7 +10,6 @@ delete network.lan
 
 set network.wan.type='bridge'
 set network.wan.proto='dhcp'
-set network.wan.accept_ra='0'
 set network.wan.auto='1'
 
 set network.client='interface'
@@ -18,7 +17,6 @@ set network.client.ifname='$lan_ifname bat0'
 set network.client.type='bridge'
 set network.client.proto='none'
 set network.client.auto='1'
-set network.client.accept_ra='1'
 
 set network.mesh='interface'
 set network.mesh.proto='batadv'