Calculator: Improve UI margin consistency

Userland/Applications/Calculator/CalculatorWindow.gml

@@ -1,5 +1,5 @@
 @GUI::Widget {
-    fixed_width: 254
+    fixed_width: 250
     fixed_height: 215
     fill_with_background_color: true
     layout: @GUI::VerticalBoxLayout
@@ -13,7 +13,7 @@
 
         @GUI::Widget {
             layout: @GUI::VerticalBoxLayout {
-                margins: [10, 2, 10, 0]
+                margins: [8, 8, 8, 8]
             }
 
             @GUI::TextBox {

Userland/Applications/Calculator/main.cpp

@@ -42,7 +42,7 @@ int main(int argc, char** argv)
     auto window = GUI::Window::construct();
     window->set_title("Calculator");
     window->set_resizable(false);
-    window->resize(254, 215);
+    window->resize(250, 215);
 
     auto& widget = window->set_main_widget<CalculatorWidget>();