Don't hardcode left-shift to disabe keyboard input on linux.

Left-shift can be used for gamepad input now.
Fixes issue 4968.

Source/Core/InputCommon/Src/ControllerInterface/Xlib/Xlib.cpp

@@ -116,8 +116,7 @@ KeyboardMouse::Key::Key(Display* const display, KeyCode keycode, const char* key
 ControlState KeyboardMouse::Key::GetState() const
 {
 	const KeyCode shift = XKeysymToKeycode(m_display, XK_Shift_L);
-	return (m_keyboard[m_keycode / 8] & (1 << (m_keycode % 8))) != 0
-			&& (m_keyboard[shift / 8] & (1 << (shift % 8))) == 0;
+	return (m_keyboard[m_keycode / 8] & (1 << (m_keycode % 8))) != 0;
 }
 
 ControlState KeyboardMouse::Button::GetState() const