swift 2.31.0 release

meta:version: 2.31.0
meta:diff-start: -
meta:series: antelope
meta:release-type: release
meta:pypi: no
meta:first: yes
meta:release:Author: Tim Burke <tim.burke@gmail.com>
meta:release:Commit: Tim Burke <tim.burke@gmail.com>
meta:release:Change-Id: I1387f1d68bc47df8babbf573573ebb925fb9420c
meta:release:Code-Review+2: Elod Illes <elod.illes@est.tech>
meta:release:Code-Review+2: Hervé Beraud <herveberaud.pro@gmail.com>
meta:release:Workflow+1: Hervé Beraud <herveberaud.pro@gmail.com>
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