Doc: Fix warnings about undocumented enum and parameters

- enum 'CaptivePortal' in QNetworkInformation::Feature
- parameter 'debug' in QNetworkAddressEntry::operator<<()
- parameter 'debug' in QNetworkInterface::operator<<()

Pick-to: 6.2
Change-Id: I518bc06edee9fa4955dc6295786ab1a6be989727
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

src/network/kernel/qnetworkinformation.cpp

@@ -445,6 +445,10 @@ QNetworkInformationBackendFactory::~QNetworkInformationBackendFactory()
         If the plugin supports this feature then
         the \c reachability property will be available.
         See also QNetworkInformation::Reachability.
+
+    \value CaptivePortal
+        If the plugin supports this feature then
+        the \c isBehindCaptivePortal property will be available.
 */
 
 /*!

src/network/kernel/qnetworkinterface.cpp

@@ -935,7 +935,7 @@ static inline QDebug flagsDebug(QDebug debug, QNetworkInterface::InterfaceFlags
    \since 6.2
 
     Writes the QNetworkAddressEntry \a entry to the stream and
-    returns a reference to the stream.
+    returns a reference to the \a debug stream.
 
     \relates QNetworkAddressEntry
  */
@@ -953,7 +953,7 @@ QDebug operator<<(QDebug debug, const QNetworkAddressEntry &entry)
 
 /*!
     Writes the QNetworkInterface \a networkInterface to the stream and
-    returns a reference to the stream.
+    returns a reference to the \a debug stream.
 
     \relates QNetworkInterface
  */