Operating systems with outdated OpenSSH are no longer supported (jenk…

…insci#1099)

List more operating systems so that web searches will find the page.

Link to the operating system end of life blog post.

Correct the name of Amazon Linux name.

Add the most important option, upgrade to a supported operating system.

README.adoc

@@ -124,11 +124,15 @@ image::images/ssh-host-key-verification.png[Configure Ssh host key verification]
 [NOTE]
 ====
 OpenSSH releases prior to link:https://www.openssh.com/txt/release-7.6[OpenSSH 7.6 (released Oct 2017)] do not support the ssh command line argument used to accept first connection.
-Red Hat Enterprise Linux 7, CentOS 7, AWS Linux 2, and Debian 9 all deliver OpenSSH releases older than OpenSSH 7.6.
+Red Hat Enterprise Linux 7, CentOS 7, Oracle Linux 7, Scientific Linux 7, Amazon Linux 2, Debian 9, and Ubuntu 16.04 all deliver OpenSSH releases older than OpenSSH 7.6.
 The "Git Host Key Verification Configuration" for those systems cannot use the "Accept first connection" strategy with command line git.
 
+Those operating systems are no longer supported by the Jenkins project.
+More details are available in the link:https://www.jenkins.io/blog/2023/05/30/operating-system-end-of-life/[end of life operating systems blog post].
+
 Users of those operating systems have the following options:
 
+* Upgrade to a supported operating system
 * Use the "Manually provided keys" host key verification strategy and provide host keys for their git hosts
 * Use the "Known hosts file" host key verification strategy and provide a known_hosts file on the agents with values for the required hosts
 * Enable JGit and use JGit instead of command line git on agents and controllers with those older OpenSSH versions