Fix naming of variables

vars/main.yml

 ---
 # vars file for hedgedocs-pad-lqdn_
 
-hedgedoc-version: "1.9.0"
-hedgedoc-sql-password : "{{ vault_service_hedgedocs_sql_password }}"
+hedgedoc_version: "1.9.0"
+hedgedoc_sql_password : "{{ vault_service_hedgedocs_sql_password }}"
 hedgedoc_session_secret : "{{ vault_hedgedoc_session_secret }}"
-hedgedocs-domain: "{{ service_hedgedocs_domain }}"
+hedgedocs_domain: "{{ service_hedgedocs_domain }}"
 hedgedoc_db_name : hedgedocs-user
 hedgedoc_db_user : hedgedocs