Use https for rpsamd key and repository

roles/mailserver/tasks/rspamd.yml

 # Installs and configures the Rspamd spam filtering system.
 
 - name: Ensure repository key for Rspamd is in place
-  apt_key: url=http://rspamd.com/apt-stable/gpg.key state=present
+  apt_key: url=https://rspamd.com/apt-stable/gpg.key state=present
   tags:
     - dependencies
 
 - name: Add Rspamd repository
-  apt_repository: repo="deb http://rspamd.com/apt-stable/ {{ ansible_distribution_release }} main"
+  apt_repository: repo="deb https://rspamd.com/apt-stable/ {{ ansible_distribution_release }} main"
   tags:
     - dependencies