Remove ui_interface ThreadSafeAskFee residue

Missed these in ca2c83d (#3415).

src/noui.cpp

@@ -34,11 +34,6 @@ static bool noui_ThreadSafeMessageBox(const std::string& message, const std::str
     return false;
 }
 
-static bool noui_ThreadSafeAskFee(int64_t /*nFeeRequired*/)
-{
-    return true;
-}
-
 static void noui_InitMessage(const std::string &message)
 {
     LogPrintf("init message: %s\n", message.c_str());
@@ -48,6 +43,5 @@ void noui_connect()
 {
     // Connect bitcoind signal handlers
     uiInterface.ThreadSafeMessageBox.connect(noui_ThreadSafeMessageBox);
-    uiInterface.ThreadSafeAskFee.connect(noui_ThreadSafeAskFee);
     uiInterface.InitMessage.connect(noui_InitMessage);
 }

src/ui_interface.h

@@ -72,9 +72,6 @@ public:
     /** Show message box. */
     boost::signals2::signal<bool (const std::string& message, const std::string& caption, unsigned int style), boost::signals2::last_value<bool> > ThreadSafeMessageBox;
 
-    /** Ask the user whether they want to pay a fee or not. */
-    boost::signals2::signal<bool (int64_t nFeeRequired), boost::signals2::last_value<bool> > ThreadSafeAskFee;
-
     /** Progress message during initialization. */
     boost::signals2::signal<void (const std::string &message)> InitMessage;