Migrate away from enums deprecated going from Qt5.12 to Qt5.15

In some instances (touched by this commit) QGC has been using enums deprecated
in Qt5.15. Enum deprecation itself appears to be a new thing (there in C++14, but
seemingly not there in C++11). We have since formally upgraded to C++17
(https://github.com/mavlink/qgroundcontrol/pull/9760), but presumably nobody
recompiled against Qt5.15 until I did, saw the errors and found myself needing
to propose this change.

The change itself is trivial and simply follows the migration notes found against
individual deprecated enums.

src/Camera/QGCCameraControl.cc

@@ -1994,7 +1994,7 @@ QGCCameraControl::_httpRequest(const QString &url)
     tempProxy.setType(QNetworkProxy::DefaultProxy);
     _netManager->setProxy(tempProxy);
     QNetworkRequest request(url);
-    request.setAttribute(QNetworkRequest::FollowRedirectsAttribute, true);
+    request.setAttribute(QNetworkRequest::RedirectPolicyAttribute, true);
     QSslConfiguration conf = request.sslConfiguration();
     conf.setPeerVerifyMode(QSslSocket::VerifyNone);
     request.setSslConfiguration(conf);

src/QGCApplication.cc

@@ -423,7 +423,7 @@ void QGCApplication::setLanguage()
             _locale = QLocale(QLocale::Korean);
             break;
         case 13:
-            _locale = QLocale(QLocale::Norwegian);
+            _locale = QLocale(QLocale::NorwegianBokmal);
             break;
         case 14:
             _locale = QLocale(QLocale::Polish);

src/Vehicle/MAVLinkLogManager.cc

@@ -743,7 +743,7 @@ MAVLinkLogManager::_sendLog(const QString& logFile)
     file->setParent(multiPart);
     QNetworkRequest request(_uploadURL);
 #if QT_VERSION > 0x050600
-    request.setAttribute(QNetworkRequest::FollowRedirectsAttribute, true);
+    request.setAttribute(QNetworkRequest::RedirectPolicyAttribute, true);
 #endif
     QNetworkReply* reply = _nam->post(request, multiPart);
     connect(reply, &QNetworkReply::finished,  this, &MAVLinkLogManager::_uploadFinished);

src/VideoManager/SubtitleWriter.cc

@@ -166,7 +166,7 @@ void SubtitleWriter::_captureTelemetry()
     stringColumns << QStringLiteral("Dialogue: 0,%1,%2,Default,,0,0,0,,{\\pos(10,35)}%3\n")
         .arg(start.toString("H:mm:ss.zzz").chopped(2))
         .arg(end.toString("H:mm:ss.zzz").chopped(2))
-        .arg(QDateTime::currentDateTime().toString(Qt::SystemLocaleShortDate));
+        .arg(QDateTime::currentDateTime().toString(QLocale::system().dateFormat(QLocale::ShortFormat)));
     // Write new data
     QTextStream stream(&_file);
     for (const auto& i : stringColumns) {