[boost] [release] 1.69.0 closed for major changes

The master branch is now closed for new libraries and breaking changes, and will be closing for the beta in one week. Also, if you're ready, you can also add your libraries' changes to the release notes at: < https://github.com/boostorg/website/blob/master/feed/history/boost_1_69_0.qb...

After editing the release notes, you should get a form to create a pull request, remember to submit it, otherwise I won't see your change. Thanks, -- The Boost Release Team