Merge bitcoin/bitcoin#29475: doc: Fix Broken Links

6fa61e3 doc: Fix Broken Links (Justin Dhillon)

Pull request description:

  ### Summery

  Here is what I have fixed:

  http://voorloopnul.com/blog/a-python-netstat-in-less-than-100-lines-of-code/
   --> https://web.archive.org/web/20190424172231/http://voorloopnul.com/blog/a-python-netstat-in-less-than-100-lines-of-code/

  ### Support my work

  These links were found with [link-inspector](https://github.com/justindhillon/link-inspector). If you find this PR useful, give the repo a ⭐

ACKs for top commit:
  fjahr:
    ACK 6fa61e3

Tree-SHA512: ba83badfc8a89f33813801f749bcd7ad41d4c9c817ece76f3bb1b60f24c28e99cfccc485a0ba059ec2c1134e8ffb5fa37fdc9835e553229ee5b1167c9b2e8d1f

Author: fanquake

test/functional/test_framework/netutil.py

@@ -4,7 +4,7 @@
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 """Linux network utilities.
 
-Roughly based on http://voorloopnul.com/blog/a-python-netstat-in-less-than-100-lines-of-code/ by Ricardo Pascal
+Roughly based on https://web.archive.org/web/20190424172231/http://voorloopnul.com/blog/a-python-netstat-in-less-than-100-lines-of-code/ by Ricardo Pascal
 """
 
 import sys