Upgrade Coturn (4.5.1.2 -> 4.5.1.3)

4.5.1.3 fixes a security vulnerability:
https://github.com/coturn/coturn/security/advisories/GHSA-c8r8-8vp5-6gcm

roles/matrix-coturn/defaults/main.yml

@@ -2,7 +2,7 @@ matrix_coturn_enabled: true
 
 matrix_coturn_container_image_self_build: false
 
-matrix_coturn_docker_image: "instrumentisto/coturn:4.5.1.2"
+matrix_coturn_docker_image: "instrumentisto/coturn:4.5.1.3"
 matrix_coturn_docker_image_force_pull: "{{ matrix_coturn_docker_image.endswith(':latest') }}"
 
 # The Docker network that Coturn would be put into.