Upgrade nginx (1.21.4 -> 1.21.5)

roles/matrix-nginx-proxy/defaults/main.yml

@@ -1,5 +1,5 @@
 matrix_nginx_proxy_enabled: true
-matrix_nginx_proxy_version: 1.21.4-alpine
+matrix_nginx_proxy_version: 1.21.5-alpine
 
 # We use an official nginx image, which we fix-up to run unprivileged.
 # An alternative would be an `nginxinc/nginx-unprivileged` image, but