Revert "Use _PROXY_MaxParallelRequestsHandler_v3 by default (#14352)" (#14420)

This reverts commit 5b680bb.

Author: Bobronium

litellm/proxy/hooks/__init__.py

@@ -17,13 +17,13 @@
 # List of all available hooks that can be enabled
 PROXY_HOOKS = {
     "max_budget_limiter": _PROXY_MaxBudgetLimiter,
-    "parallel_request_limiter": _PROXY_MaxParallelRequestsHandler_v3,
+    "parallel_request_limiter": _PROXY_MaxParallelRequestsHandler,
     "cache_control_check": _PROXY_CacheControlCheck,
 }
 
 ## FEATURE FLAG HOOKS ##
-if os.getenv("LEGACY_MULTI_INSTANCE_RATE_LIMITING", "false").lower() == "true":
-    PROXY_HOOKS["parallel_request_limiter"] = _PROXY_MaxParallelRequestsHandler
+if os.getenv("EXPERIMENTAL_MULTI_INSTANCE_RATE_LIMITING", "false").lower() == "true":
+    PROXY_HOOKS["parallel_request_limiter"] = _PROXY_MaxParallelRequestsHandler_v3
 
 
 ### update PROXY_HOOKS with ENTERPRISE_PROXY_HOOKS ###