luci-{app,proto}-wireguard: remove kmod-wireguard

Prepares for 5.10 migration. wireguard-tools will bring in the correct
wireguard kernel module dependency - either kmod-wireguard or
kmod-wireguard-oot.

Depends on https://github.com/openwrt/openwrt/pull/3885

Signed-off-by: Ilya Lipnitskiy <ilya.lipnitskiy@gmail.com>