Rename Element configuration key (preferredDomain -> preferred_domain)

Related to: https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2375#issuecomment-1655758296

roles/custom/matrix-base/templates/static-files/well-known/matrix-client.j2

@@ -20,10 +20,10 @@
 	{% endif %}
 	{% if matrix_client_element_jitsi_preferredDomain %},
 	"io.element.jitsi": {
-		"preferredDomain": {{ matrix_client_element_jitsi_preferredDomain|to_json }}
+		"preferred_domain": {{ matrix_client_element_jitsi_preferredDomain|to_json }}
 	},
 	"im.vector.riot.jitsi": {
-		"preferredDomain": {{ matrix_client_element_jitsi_preferredDomain|to_json }}
+		"preferred_domain": {{ matrix_client_element_jitsi_preferredDomain|to_json }}
 	}
 	{% endif %}
 	{% if matrix_sliding_sync_enabled %},

roles/custom/matrix-client-element/templates/config.json.j2

@@ -35,7 +35,7 @@
 	},
 	{% if matrix_client_element_jitsi_preferredDomain %}
 	"jitsi": {
-        "preferredDomain": {{ matrix_client_element_jitsi_preferredDomain | to_json }}
+        "preferred_domain": {{ matrix_client_element_jitsi_preferredDomain | to_json }}
     },
 	{% endif %}
 	{% if matrix_client_element_location_sharing_enabled %}