Fix typo in variable name

Regression since bfc5374fc8

group_vars/matrix_servers

@@ -1969,10 +1969,10 @@ matrix_mautrix_whatsapp_appservice_token: "{{ '%s' | format(matrix_homeserver_ge
 matrix_mautrix_whatsapp_homeserver_address: "{{ matrix_addons_homeserver_client_api_url }}"
 matrix_mautrix_whatsapp_homeserver_token: "{{ '%s' | format(matrix_homeserver_generic_secret_key) | password_hash('sha512', 'whats.hs.token', rounds=655555) | to_uuid }}"
 
-matrix_mautrix_slack_double_puppet_secrets_auto: |-
+matrix_mautrix_whatsapp_double_puppet_secrets_auto: |-
   {{
     {
-      matrix_mautrix_slack_homeserver_domain: ("as_token:" + matrix_appservice_double_puppet_registration_as_token)
+      matrix_mautrix_whatsapp_homeserver_domain: ("as_token:" + matrix_appservice_double_puppet_registration_as_token)
     }
     if matrix_appservice_double_puppet_enabled
     else {}