Core: Remove host thread assert in PauseAndLock().

Fixing all the places it's used turned out to be a more complicated task than anticipated. So let's remove this for now so we don't confuse users with cryptic error messages...

Source/Core/Core/Core.cpp

@@ -796,7 +796,6 @@ void SaveScreenShot(std::string_view name)
 static bool PauseAndLock(Core::System& system, bool do_lock, bool unpause_on_unlock)
 {
   // WARNING: PauseAndLock is not fully threadsafe so is only valid on the Host Thread
-  ASSERT(IsHostThread());
 
   if (!IsRunningAndStarted())
     return true;