Document version 2.11.10 in the changelog
Document version 2.11.10 in the changelog

Even though it's not part of this branch, document version 2.11.10 in
the changelog. It can be found on the `2-11-stable` branch. The change
in this version (PR #736) was a backport of the same change in version
3.0.3 (PR #720).

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appsignal/appsignal-ruby,appsignal/appsignal-ruby,appsignal/appsignal-ruby,appsignal/appsignal-ruby