Bump wagtail from 2.9.3 to 2.10
Bump wagtail from 2.9.3 to 2.10

Bumps [wagtail](https://github.com/wagtail/wagtail) from 2.9.3 to 2.10.
- [Release notes](https://github.com/wagtail/wagtail/releases)
- [Changelog](https://github.com/wagtail/wagtail/blob/master/CHANGELOG.txt)
- [Commits](https://github.com/wagtail/wagtail/compare/v2.9.3...v2.10)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
marteinn/wagtail-alt-generator,marteinn/wagtail-alt-generator,marteinn/wagtail-alt-generator