Replace X11 enter key

Tester @Goofybud on Debian reported that the enter button did not work.
There are apparently 4 different enter buttons in X11:
    XK_Linefeed
    XK_Return
    XK_KP_Enter
    XK_ISO_Enter

I am attempting XK_Return because it seems like the most obvious next
attempt.

src/tabcontrollers/keyboardinput/KeyboardInputX11.cpp

@@ -50,7 +50,7 @@ void sendKeyboardInput( QString input )
 
 void sendKeyboardEnter()
 {
-    sendKeyPress( XK_ISO_Enter, noModifier );
+    sendKeyPress( XK_Return, noModifier );
 }
 
 void sendKeyboardBackspace( const int count )
@@ -68,7 +68,7 @@ void sendKeyboardAltTab()
 
 void sendKeyboardAltEnter()
 {
-    sendKeyPress( XK_ISO_Enter, XK_Alt_L );
+    sendKeyPress( XK_Return, XK_Alt_L );
 }
 
 void sendMediaNextSong()