Deprecate class KNTLM & methods, no users known outside of kio-http
While some projects list KF5::KIONTLM in the link libraries, they do not include either the header khtml.h or the CamelCase forward header currently only provided by kdelibssupport4. See https://lxr.kde.org/search?%21v=kf5-qt5&_filestring=&_string=kntlm.h&_casesensitive=1 and https://lxr.kde.org/search?%21v=kf5-qt5&_filestring=&_string=NTLM&_casesensitive=1