Simplify KDE4 yielding.

QAbstractEventDispatcher::processEvents always processes all
pending events, so we can ignore the the second Yield parameter
(bHandleAllCurrentEvents).

Change-Id: I49a70ed13d0215b89f48eed93d78eef2f083dc0d
Reviewed-on: https://gerrit.libreoffice.org/6686
Reviewed-by: Thorsten Behrens <thb@documentfoundation.org>
Tested-by: Thorsten Behrens <thb@documentfoundation.org>