Update concurrency value to be lambda since not set in env (#297)

Author: justinwlin

serverless/development/dual-mode-worker.mdx

@@ -96,7 +96,7 @@ if mode_to_run == "pod":
 else: 
     runpod.serverless.start({
         "handler": handler,
-        "concurrency_modifier": adjust_concurrency,
+        "concurrency_modifier": lambda current: 1,
     })
 
 ```