fix: Makefile shall pull sandbox:main, not :latest (#2561)

Makefile

@@ -2,7 +2,7 @@ SHELL=/bin/bash
 # Makefile for OpenDevin project
 
 # Variables
-DOCKER_IMAGE = ghcr.io/opendevin/sandbox
+DOCKER_IMAGE = ghcr.io/opendevin/sandbox:main
 BACKEND_PORT = 3000
 BACKEND_HOST = "127.0.0.1:$(BACKEND_PORT)"
 FRONTEND_PORT = 3001