Add EOL mention to 3.0.x across related home pages

For the elasticsearch page, remove 2.16 which was previously deemed EOL.

Add missing 3.3 mention to the hereby amended support page.

[1] https://www.gerritcodereview.com/2020-09-07-gerrit-3.3-release-plan.html#end-of-life-for-gerrit-30x

Change-Id: I791df30659397e5899752524216bce4b25450efd
3 files changed