doc: update mailing list address

Move from sourceforge to linux foundation.

Also get rid of some other stale mentions of sourceforge.

README.md

@@ -34,7 +34,7 @@ development team members simply pulls it.
 
 If it is a *more complicated or potentially controversial* change, then the patch
 submitter will be asked to start a discussion (if they haven't already) on the
-[mailing list](http://sourceforge.net/mailarchive/forum.php?forum_name=bitcoin-development).
+[mailing list](https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev)
 
 The patch will be accepted if there is broad consensus that it is a good thing.
 Developers should expect to rework and resubmit patches if the code doesn't