VST3 Client: Fix leak caused by unnecessary manual refcounting

In older versions of the VST3SDK, hostContext is a raw pointer,
in newer versions it's a smart pointer. If we do manual
refcounting with the smart pointer, we may cause leaks.

modules/juce_audio_plugin_client/VST3/juce_VST3_Wrapper.cpp

@@ -652,16 +652,8 @@ public:
     tresult PLUGIN_API initialize (FUnknown* context) override
     {
         if (hostContext != context)
-        {
-            if (hostContext != nullptr)
-                hostContext->release();
-
             hostContext = context;
 
-            if (hostContext != nullptr)
-                hostContext->addRef();
-        }
-
         return kResultTrue;
     }