chore: update to v12 beta 6 #2524

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@maribethb

The following contributors were found for this pull request:

✅ ad8ce93 Author: @maribethb <ma*****hb@google.com>
✅ 144b6d0 Author: @gonfunko <ad****n@google.com>
✅ 43bdfab Author: @cpcallen <cpc******git@google.com>
✅ d5eb18f Author: @BenHenning <bh****ng@google.com>
✅ f98d974 Author: @RoboErikG <ep****rn@google.com>, <RoboErikG@users.noreply.github.com>

(Only the first commit for a unique contributor is listed.)