🔠 No case conversion for SIP003 environment variables

- Corrects the mistake in 127cb96 and fixes #3013

shadowsocks-csharp/Controller/Service/Sip003Plugin.cs

@@ -122,13 +122,12 @@ namespace Shadowsocks.Controller.Service
 
         public string ExpandEnvironmentVariables(string name, StringDictionary environmentVariables = null)
         {
-            name = name.ToLower();
             // Expand the environment variables from the new process itself
             if (environmentVariables != null)
             {
                 foreach(string key in environmentVariables.Keys)
                 {
-                    name = name.Replace($"%{key.ToLower()}%", environmentVariables[key]);
+                    name = name.Replace($"%{key}%", environmentVariables[key]);
                 }
             }
             // Also expand the environment variables from current main process (system)