Use the 'public' part of the TSIG key

We're using HMAC so all is needed is a shared secret.

roles/float-infra-acme/templates/config.yml.j2

@@ -12,7 +12,7 @@ dns:
   enabled: true
   tsig_key_name: "acme."
   tsig_key_algo: "{{ acme_tsig_key.algo | lower }}."
-  tsig_key_secret: "{{ acme_tsig_key.private }}"
+  tsig_key_secret: "{{ acme_tsig_key.public }}"
   nameservers:
 {% for h in services['dns'].hosts | sort %}
     - {{ h }}.dns.{{ domain }}