[plugin entryproperties] removed cache from serendipity['entry'] arra…

Created by: stephanbrunker

…y, is already in subarray

While debugging, i discovered that the entry data is three times in the 'entry' array: One time in [body] etc, one time in the properties subarray as ep_cache and a third time the same cache directly in the array. The last one is unnecessary because the fetch_entries function put it already there, no need to use the fetchentries event hook to put it there a second time.