Qt/Config: Fix inconsistent spacing between options

Source/Core/DolphinQt2/Config/Graphics/AdvancedWidget.cpp

@@ -100,6 +100,7 @@ void AdvancedWidget::CreateWidgets()
   main_layout->addWidget(debugging_box);
   main_layout->addWidget(utility_box);
   main_layout->addWidget(misc_box);
+  main_layout->addStretch();
 
   setLayout(main_layout);
 }

Source/Core/DolphinQt2/Config/Graphics/EnhancementsWidget.cpp

@@ -113,6 +113,7 @@ void EnhancementsWidget::CreateWidgets()
 
   main_layout->addWidget(enhancements_box);
   main_layout->addWidget(stereoscopy_box);
+  main_layout->addStretch();
 
   setLayout(main_layout);
 }

Source/Core/DolphinQt2/Config/Graphics/GeneralWidget.cpp

@@ -116,6 +116,7 @@ void GeneralWidget::CreateWidgets()
 
   main_layout->addWidget(m_video_box);
   main_layout->addWidget(m_options_box);
+  main_layout->addStretch();
 
   setLayout(main_layout);
 }

Source/Core/DolphinQt2/Config/Graphics/HacksWidget.cpp

@@ -94,6 +94,7 @@ void HacksWidget::CreateWidgets()
   main_layout->addWidget(texture_cache_box);
   main_layout->addWidget(xfb_box);
   main_layout->addWidget(other_box);
+  main_layout->addStretch();
 
   setLayout(main_layout);
 }

Source/Core/DolphinQt2/Config/Graphics/SoftwareRendererWidget.cpp

@@ -99,6 +99,7 @@ void SoftwareRendererWidget::CreateWidgets()
   main_layout->addWidget(overlay_box);
   main_layout->addWidget(utility_box);
   main_layout->addWidget(object_range_box);
+  main_layout->addStretch();
 
   setLayout(main_layout);
 }