Use empty string for default Sentry DSN variables

Both should work identically, but an empty string seems better

roles/custom/matrix-jitsi/defaults/main.yml

@@ -206,7 +206,7 @@ matrix_jitsi_jicofo_auth_user: focus
 matrix_jitsi_jicofo_auth_password: ''
 
 # To enable Sentry integration for Jicofo, specify a valid DSN connection string
-matrix_jitsi_jicofo_sentry_dsn: 0
+matrix_jitsi_jicofo_sentry_dsn: ''
 
 matrix_jitsi_jvb_docker_image: "{{ matrix_container_global_registry_prefix }}jitsi/jvb:{{ matrix_jitsi_container_image_tag }}"
 matrix_jitsi_jvb_docker_image_force_pull: "{{ matrix_jitsi_jvb_docker_image.endswith(':latest') }}"
@@ -224,7 +224,7 @@ matrix_jitsi_jvb_auth_user: jvb
 matrix_jitsi_jvb_auth_password: ''
 
 # To enable Sentry integration for JVB, specify a valid DSN connection string
-matrix_jitsi_jvb_sentry_dsn: 0
+matrix_jitsi_jvb_sentry_dsn: ''
 
 # STUN servers used by JVB on the server-side, so it can discover its own external IP address.
 # Pointing this to a STUN server running on the same Docker network may lead to incorrect IP address discovery.