Fix links in Javadoc and reference docs

- Fix broken links (by using a new URL, an alternative URL, or a
  Wayback Machine link)

- Use HTTPS where possible

- Remove https://issuetracker.springsource.com/browse/EBR-349: this
  link is dead and is also mentioned in
  https://jira.spring.io/browse/SPR-8093

- Clean up nohttp allowlist.lines

Closes gh-28876

src/nohttp/allowlist.lines

@@ -1,26 +1,7 @@
 ^http://aopalliance.sourceforge.net.*
-^http://[^/]*caucho.com.*
-^http://cglib.sourceforge.net.*
-^http://classdoc.sourceforge.net.*
-^http://easymock.org.*
-^http://forum.thymeleaf.org.*
-^http://[^/]*gebish.org.*
-^http://[^/]*groovy-lang.org.*
-^http://[^/]*hsqldb.org.*
-^http://htmlunit.sourceforge.net.*
-^http://javadiff.cvs.sourceforge.net.*
-^http://javadiff.sourceforge.net.*
 ^http://jibx.sourceforge.net.*
-^http://jotm.objectweb.org.*
-^http://json-b.net/.*
 ^http://mx4j.sourceforge.net.*
 ^http://objenesis.org.*
-^http://reactivex.io.*
-^http://sites.utoronto.ca.*
-^http://www.beanshell.org.*
-^http://www.doclet.com.*
-^http://www.jensgulden.de.*
 ^http://www.mockobjects.com.*
 ^http://www.w3.org/2000/xmlns/
-^http://xmlunit.sourceforge.net.*
 ^http://xunitpatterns.com.*