Core: Remove Unused IsRunningInCurrentThread Function

Source/Core/Core/Core.h

@@ -138,9 +138,8 @@ void UndeclareAsHostThread();
 std::string StopMessage(bool main_thread, std::string_view message);
 
 bool IsRunning();
-bool IsRunningAndStarted();       // is running and the CPU loop has been entered
-bool IsRunningInCurrentThread();  // this tells us whether we are running in the CPU thread.
-bool IsCPUThread();               // this tells us whether we are the CPU thread.
+bool IsRunningAndStarted();  // is running and the CPU loop has been entered
+bool IsCPUThread();          // this tells us whether we are the CPU thread.
 bool IsGPUThread();
 bool IsHostThread();