clazy: Use 4-arg connect in videosource.

Clazy recommends using the 4-arg variant of Object::connect over the
3-arg version. The main reason for this is that the signal will not be
called if the target object has been deleted.

In this instance, it appears clear that the target object is the
current object, since the lambda is referencing variables in the
CardInput class.

https://github.com/KDE/clazy/blob/master/docs/checks/README-connect-3arg-lambda.md

mythtv/libs/libmythtv/videosource.cpp

@@ -3396,7 +3396,7 @@ void CardInput::channelScanner(void)
 
     if (ssd->Create())
     {
-        connect(ssd, &StandardSettingDialog::Exiting,
+        connect(ssd, &StandardSettingDialog::Exiting, this,
                 [=]()
                 {
                     if (SourceUtil::GetChannelCount(srcid))