Fixed DB names not matching in the containers

Changed MySQL hostname in the nignxproxymanager image to match the name of the MariaDB container

docker-compose/nginxproxymanager/docker-compose.yaml

@@ -13,7 +13,7 @@ services:
       - '81:81'
       - '443:443'
     environment:
-      DB_MYSQL_HOST: "db"
+      DB_MYSQL_HOST: "nginxproxymanager-db"
       DB_MYSQL_PORT: 3306
       DB_MYSQL_USER: "npm"
       DB_MYSQL_PASSWORD: "npm"
@@ -29,4 +29,4 @@ services:
       MYSQL_USER: 'npm'
       MYSQL_PASSWORD: 'npm'
     volumes:
-      - nginxproxymanager-db:/var/lib/mysql
+      - nginxproxymanager-db:/var/lib/mysql