doc: update mailing list address

Move from sourceforge to linux foundation.

Also get rid of some other stale mentions of sourceforge.

Github-Pull: #6319
Rebased-From: 88d8525ca2ff2afc171cd0f625a098371f3a6af5

contrib/debian/copyright

@@ -2,8 +2,7 @@ Format: http://svn.debian.org/wsvn/dep/web/deps/dep5.mdwn?rev=174
 Upstream-Name: Bitcoin
 Upstream-Contact: Satoshi Nakamoto <satoshin@gmx.com>
  irc://#bitcoin@freenode.net
-Source: http://sourceforge.net/projects/bitcoin/files/
- https://github.com/bitcoin/bitcoin
+Source: https://github.com/bitcoin/bitcoin
 
 Files: *
 Copyright: 2009-2012, Bitcoin Core Developers

contrib/gitian-downloader/linux-download-config

@@ -3,7 +3,7 @@ name: bitcoin
 urls:
 - http://bitcoin.org/bitcoin-latest-linux-gitian.zip
 rss:
-- url: http://sourceforge.net/api/file/index/project-id/244765/mtime/desc/limit/100/rss
+- url: 
   xpath: //item/link/text()
   pattern: bitcoin-\d+.\d+.\d+-linux-gitian.zip
 signers:

contrib/gitian-downloader/win32-download-config

@@ -3,7 +3,7 @@ name: bitcoin
 urls:
 - http://bitcoin.org/bitcoin-latest-win32-gitian.zip
 rss:
-- url: http://sourceforge.net/api/file/index/project-id/244765/mtime/desc/limit/100/rss
+- url: 
   xpath: //item/link/text()
   pattern: bitcoin-\d+.\d+.\d+-win32-gitian.zip
 signers: