Gutenberg: v18.9.x plugin upgrade

[gutenberg-plugin-upgrade-bot]

Previous upgrade: #92543
Release notes: v18.9.0

Install and activate

• Install and activate v18.9.0-rc.1 on edge (D157076-code)
• Install and activate v18.9.0 on edge (D157527-code)
• Activate v18.9.0 on production (D157528-code)
• Request v18.9.0 AT upgrade (https://github.com/Automattic/gutenberg-dotcom-woa-releases/releases/tag/v18.9.0)

Testing

• v18.9.0 Desktop viewport E2E
• v18.9.0 Mobile viewport E2E
• v18.9.0 WPCOM core (D157528-code)

Publish internal announcements

• Slack: #team-calypso (p1723117652517959-slack-C7YPUHBB2)
• Slack: #dotcom-happy-announce (p1723115226687039-slack-CB0B2G43X)
• P2: wpcomhappy (p7DVsv-lec-p2)

Wrap-up

• Clean up unused releases
• Add log entry to the Gutenberg Upgrade Log (pcoGjb-g-p2)
• Open a new issue for the next upgrade, transfer remaining tasks, close this issue.

Blockers 🤷‍♀️

Other Issues 🐛

Issues transferred from previous release(s)

• https://github.com/Automattic/dotcom-forge/issues/8007 (carried over from 18.6.0)
• The Dotcom tracking events for block insertion in the editor are not working due to GB changes. (p1721791447737549-slack-CBTN58FTJ)

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cc @Automattic/gutenberg-upgrades

[gutenberg-plugin-upgrade-bot]

Automated update:

• v18.9.0-rc.1 activation on edge marked as complete.
• Release notes updated to v18.9.0-rc.1
• Updated the diff used for v18.9.0-rc.1 core tests

[gutenberg-plugin-upgrade-bot]

Automated update:

• v18.9.0 activation on edge marked as complete.
• Release notes updated to v18.9.0

[gutenberg-plugin-upgrade-bot]

Automated update:
v18.9.0 is available at https://github.com/Automattic/gutenberg-dotcom-woa-releases/releases/tag/v18.9.0 for AT to pick up.