If the the response is chunk-encoded, ignore the Content-Length

If the the response is chunk-encoded, ignore the Content-Length

... header sent by the server.

Allows to load https://redmine.lighttpd.net/ with filtering enabled.

Previously requests would fail with complaints like:

   2021-03-20 14:02:08.924 619000011880 Connect: Done reading from server. Expected content length: 7235. Actual content length: 7243. Bytes most recently read: 8130.
   2021-03-20 14:02:08.924 619000011880 Re-Filter: Need to de-chunk first
   2021-03-20 14:02:08.924 619000011880 Error: Not enough room for trailing CRLF.
   2021-03-20 14:02:08.925 619000011880 Connect: Received 7243 bytes while expecting 7235.
   2021-03-20 14:02:08.925 619000011880 Connect: Marking the server socket 8 tainted.

Privoxy would then forward a partialy de-chunked response with
trailing garbage without removing the Transfer-Encoding header.