Disable use of Qt APIs deprecated in 5.15.0 and earlier versions (#4133)

src/widgets/dialogs/SettingsDialog.cpp

@@ -123,7 +123,7 @@ void SettingsDialog::initUi()
         .assign(&this->ui_.pageStack)
         .withoutMargin();
 
-    this->ui_.pageStack->setMargin(0);
+    this->ui_.pageStack->setContentsMargins(0, 0, 0, 0);
 
     outerBox->addSpacing(12);
 
@@ -193,9 +193,7 @@ void SettingsDialog::filterElements(const QString &text)
 
 void SettingsDialog::addTabs()
 {
-    this->ui_.tabContainer->setMargin(0);
     this->ui_.tabContainer->setSpacing(0);
-
     this->ui_.tabContainer->setContentsMargins(0, 20, 0, 20);
 
     // Constructors are wrapped in std::function to remove some strain from first time loading.