Suppress ACTIONS_CACHE_SERVICE_V2 variable

We want `actions/cache` to use cache service v1 instead of v2 until we
add v2 support to our transparent cache proxy.

Author: enescakir

src/Runner.Worker/Handlers/NodeScriptActionHandler.cs

@@ -83,7 +83,7 @@ public async Task RunAsync(ActionRunStage stage)
             }
             if (ExecutionContext.Global.Variables.GetBoolean("actions_uses_cache_service_v2") ?? false)
             {
-                Environment["ACTIONS_CACHE_SERVICE_V2"] = bool.TrueString;
+                Environment["REAL_ACTIONS_CACHE_SERVICE_V2"] = bool.TrueString;
             }
 
             // Resolve the target script.