RFC: Shorten KSycoca update delay

Currently kded waits 10 seconds before KSycoca is updated. This is a very long and user noticeable time, for example on a fresh system without a browser after installing one it will take that long after the process is finished until the icon appears in the default Plasma panel. Historically the timeout was changed in in the before times in both directions, see kdelibs commits https://commits.kde.org/unmaintained/kdelibs/f8b972cbc797dca46e63072248cee0daec78f46f https://commits.kde.org/unmaintained/kdelibs/cc93a95616c8f4d24941dc2ebe1837327153dc3b https://commits.kde.org/unmaintained/kdelibs/f6ae8d6490f5b0cf18b92337405971018ff568aa It seems the intention is to batch events together that come in bursts for example during a system update. A shorter timer will still achieve the same goal, the wait period starts anew on every change and subsequent call to QTimer::start. The difference is the delay between when everything has calmed down to when KSyCoca is updated.