Layouts: Add/remove contentMargins where needed

Some cases were preexisting, some were introduced recently

Change-Id: I0e7e7b74422c420fbf4563d7cbf384e53931c3a0
Reviewed-by: hjk <hjk@qt.io>

src/plugins/cppcheck/cppcheckoptions.cpp

@@ -130,6 +130,7 @@ public:
 
         auto vbox = new QVBoxLayout(this);
         vbox->addWidget(m_optionWidget);
+        vbox->setContentsMargins(0, 0, 0, 0);
 
         m_optionWidget->load(m_page->m_tool.options());
     }