Make it compile against last qt5.15 without deprecated method

src/kmlaunchexternalcomponent.cpp

@@ -75,7 +75,7 @@ void KMLaunchExternalComponent::slotConfigureFollowupReminder()
 
 void KMLaunchExternalComponent::slotStartCertManager()
 {
-    if (!QProcess::startDetached(QStringLiteral("kleopatra"))) {
+    if (!QProcess::startDetached(QStringLiteral("kleopatra"), QStringList())) {
         KMessageBox::error(mParentWidget, i18n("Could not start certificate manager; "
                                                "please make sure you have Kleopatra properly installed."),
                            i18n("KMail Error"));
@@ -85,7 +85,7 @@ void KMLaunchExternalComponent::slotStartCertManager()
 void KMLaunchExternalComponent::slotImportWizard()
 {
     const QString path = QStandardPaths::findExecutable(QStringLiteral("akonadiimportwizard"));
-    if (!QProcess::startDetached(path)) {
+    if (!QProcess::startDetached(path, QStringList())) {
         KMessageBox::error(mParentWidget, i18n("Could not start the import wizard. "
                                                "Please make sure you have ImportWizard properly installed."),
                            i18n("Unable to start import wizard"));
@@ -95,7 +95,7 @@ void KMLaunchExternalComponent::slotImportWizard()
 void KMLaunchExternalComponent::slotExportData()
 {
     const QString path = QStandardPaths::findExecutable(QStringLiteral("pimdataexporter"));
-    if (!QProcess::startDetached(path)) {
+    if (!QProcess::startDetached(path, QStringList())) {
         KMessageBox::error(mParentWidget, i18n("Could not start \"PIM Data Exporter\" program. "
                                                "Please check your installation."),
                            i18n("Unable to start \"PIM Data Exporter\" program"));

src/kmmainwidget.cpp

@@ -323,7 +323,7 @@ KMMainWidget::KMMainWidget(QWidget *parent, KXMLGUIClient *aGUIClient, KActionCo
         if (!listOfMailerFound.isEmpty()) {
             if (KMessageBox::questionYesNoList(this, i18n("Another mailer was found on system. Do you want to import data from it?"), listOfMailerFound) == KMessageBox::Yes) {
                 const QString path = QStandardPaths::findExecutable(QStringLiteral("akonadiimportwizard"));
-                if (!QProcess::startDetached(path)) {
+                if (!QProcess::startDetached(path, QStringList())) {
                     KMessageBox::error(this, i18n("Could not start the import wizard. "
                                                   "Please check your installation."),
                                        i18n("Unable to start import wizard"));