doc: mark Node.js 13 as End-of-Life

Remove the "Current" label for Node.js 13 in the CHANGELOG.

PR-URL: https://github.com/nodejs/node/pull/34436


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Beth Griggs <Bethany.Griggs@uk.ibm.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Myles Borins <myles.borins@gmail.com>