Update README.md - fixing docker compose command (jaegertracing#4444)

The correct command is "docker compose up" and not "docker-compose up"
Reference: https://docs.docker.com/engine/reference/commandline/compose/

Signed-off-by: Rony Aurora <78105687+tqi-raurora@users.noreply.github.com>

docker-compose/monitor/README.md

@@ -29,8 +29,8 @@ The following diagram illustrates the relationship between these components:
 ## Bring up/down the dev environment
 
 ```bash
-docker-compose up
-docker-compose down
+docker compose up
+docker compose down
 ```
 
 **Tips:**