chore(deps): update dependency wagtail to v2.16.3

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
wagtail (source, changelog)	==2.16.2 -> ==2.16.3

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Release Notes

wagtail/wagtail

v2.16.3

Compare Source

• Fix: Ensure the upgrade notification request for the latest release, which can be disabled via the WAGTAIL_ENABLE_UPDATE_CHECK sends the referrer origin with strict-origin-when-cross-origin (Karl Hobley)
• Fix: On the Locked Pages report, limit the "locked by" filter to just users who have locked pages (Stefan Hammer)
• Fix: Ensure Python 3.10 compatibility when using Elasticsearch backend (Przemysław Buczkowski, Matt Westcott)

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