applets/window-list: use new popup placement enum
The window-list applet still uses the old location for the popup placement enum (in PlasmaCore.Types), rather than its new home in PlasmaExtras.Menu. As the old one is no longer defined, this may lead to a misaligned popup menu, and definitely to a runtime error.
This change adapts the applet to the new way of accessing the popup placement types.
(cherry picked from commit b0a8a617)
Co-authored-by: Christoph Wolk christoph.wolk@gmx.de