convert/svn: do not retrieve removed files It gives us a way to not retrieve content of entries we know are no longer files. And it is faster when converting remote repositories.

convert/svn: correctly encode deleted entry paths This recode call was removed in ede2247e61aa, because it looked the encode(decode()) construct was a no-op. In fact, the first decode() call was wrong, and entries still have to be encoded before being passed to the sink.

convert/svn: remove broken but unused copy filtering code For some reason, if a copy source is deleted in the same revision it is referenced, it is filtered out. This is silly, because this happens all the time with move operations. Fortunately, the filtering code is buggy and ends being a no-op 99% of the time, since it does not delete the right key. Just remove all this nonsense.