LibGUI: Remove parent parameter to GUI::Widget constructor

Author: https://github.com/awesomekling
Commit: c5d913970a

Libraries/LibGUI/Slider.cpp

@@ -33,14 +33,8 @@
 
 namespace GUI {
 
-Slider::Slider(Widget* parent)
-    : Slider(Orientation::Horizontal, parent)
-{
-}
-
-Slider::Slider(Orientation orientation, Widget* parent)
-    : Widget(parent)
-    , m_orientation(orientation)
+Slider::Slider(Orientation orientation)
+    : m_orientation(orientation)
 {
 }