Doc: Add missing comma

Fixes: QTBUG-95379
Pick-to: 6.2
Change-Id: Ie66feccff27d055a4ebd4f7b26313910934ad234
Reviewed-by: Nico Vertriest <nico.vertriest@qt.io>

src/corelib/text/qstringlist.cpp

@@ -108,7 +108,7 @@ QT_BEGIN_NAMESPACE
     \section1 Adding Strings
 
     Strings can be added to a list using the \l
-    {QList::insert()}{insert()} \l
+    {QList::insert()}{insert()}, \l
     {QList::append()}{append()}, \l
     {QList::operator+=()}{operator+=()} and \l
     {operator<<()} functions.