Remove doNotManage hack for Java Applets

The hack used to be used to hide windows before they get embedded into
another window. This has been wrong on multiple levels:
1. it does not belong into a window manager - the window should take care
of this by itself
2. Window title is not a proper way to identify windows
3. Using D-Bus to inform an X11 window manager about windows which should
not get managed is rather strange
4. The hack only works with KWin, but not with any other X Window Manager
5. Windows identified with this hack still appear in Alt+Tab, that is
they are managed after all. Only a flicker is suppressed
6. Such windows are shown in the taskbar which nicely illustrates how
wrong a D-Bus call to the window manager is

That the hack has been introduced for Java Applets in KHTML also shows
that this is wrong. Why does Gecko and WebKit not need such a hack? Why
is KHTML tied so closely to X11 and KWin? Having a hack for a technology
which is obsoleted (Java Applets) and shouldn't be used due to security
issues is another reason to no longer support this hack. This usage has
been removed from KHTML as of 67939b1 of kdelibs git repo.

REVIEW: 109450