wireguard-tools: Remove hard dependency to wireguard-module

The default Linux kernel for dunfell is 5.4 and the wireguard module was
added upstream in 5.6. Thus dunfell uses an external module to provide
wireguard.

We use the Linux kernel 5.10 for some time now and enabled wireguard.
The wireguard-module is not needed anymore so remove it and us the
kernel-module-wireguard instead.

See also
http://cgit.openembedded.org/meta-openembedded/commit/meta-networking/recipes-kernel/wireguard?id=63ebd02d22784519efb31273832e69476b0c8b64

recipes-kernel/wireguard/wireguard-tools_1.0.20200319.bbappend

+DEPENDS_remove = "wireguard-module"
+
+RDEPENDS_${PN} = "bash"
+RRECOMMENDS_${PN} = "kernel-module-wireguard"
+