[doc][trivial] Remove source forge from Debian watch.

contrib/debian/watch

@@ -1,7 +1,5 @@
 # Run the "uscan" command to check for upstream updates and more.
 version=3
 # use qa.debian.org redirector; see man uscan
-opts=uversionmangle=s/(\d)(alpha|beta|rc)/$1~$2/;s/\-src//,dversionmangle=s/~dfsg\d*// \
- http://sf.net/bitcoin/bitcoin-(\d.*)-linux\.tar\.gz debian
 opts=uversionmangle=s/(\d)(alpha|beta|rc)/$1~$2/,dversionmangle=s/~dfsg\d*// \
  http://githubredir.debian.net/github/bitcoin/bitcoin v(.*).tar.gz