gpu_thread: Remove unused dma_pusher class member variable from ThreadManager

The pusher instance is only ever used in the constructor of the
ThreadManager for creating the thread that the ThreadManager instance
contains. Aside from that, the member is unused, so it can be removed.

src/video_core/gpu_thread.h

@@ -4,10 +4,8 @@
 
 #pragma once
 
-#include <array>
 #include <atomic>
 #include <condition_variable>
-#include <memory>
 #include <mutex>
 #include <optional>
 #include <thread>
@@ -177,7 +175,6 @@ private:
 private:
     SynchState state;
     VideoCore::RendererBase& renderer;
-    Tegra::DmaPusher& dma_pusher;
     std::thread thread;
     std::thread::id thread_id;
 };