systemd: Disable DNS over TLS

Fix the error, that `gnutls/socket.h` cannot be found.

    ../source/src/resolve/resolved-dns-transaction.c:17:10: fatal error: gnutls/socket.h: No such
     file or directory
     #include <gnutls/socket.h>
              ^~~~~~~~~~~~~~~~~
    compilation terminated.

[1]: https://github.com/systemd/systemd/issues/9403
[2]: https://github.com/systemd/systemd/pull/9410

systemd.be0

@@ -60,6 +60,7 @@ mee_configure() {
         -Dblkid=true \
         -Dbuildtype=release \
         -Ddefault-dnssec=yes \
+        -Ddns-over-tls=false \
         -Ddns-servers='141.14.16.1' \
         -Dntp-servers='zeit.fu-berlin.de ntps1-0.cs.tu-berlin.de time.fu-berlin.de' \
         -Dfirstboot=false \