[boost] [website] Update notes of historic releases

Hi, Is this possible to update release notes of historic releases? I'd like to update notes of GIL for 1.69 which, as I found, have been never collected and are completely missing https://github.com/boostorg/gil/commit/2ff2d31895dae665ef3e05d0496bc082470e2... Best regards, -- Mateusz Loskot, http://mateusz.loskot.net