git: openjdk/leyden: premain: Update JEP titles, and add a general warning that flags will be renamed

[Mark Reinhold]

Changeset: 864228c7
Branch: premain
Author:    Mark Reinhold <mr at openjdk.org>
Date:      2024-08-15 18:07:06 +0000
URL:       https://git.openjdk.org/leyden/commit/864228c7c494e7d46ab653eaacaacb8169dd34df

Update JEP titles, and add a general warning that flags will be renamed

! README.md