Security releases - 4.1.9 (LTS), 5.0.5 and 5.1.3

[gasman]

Wagtail releases 4.1.9 (LTS), 5.0.5 and 5.1.3 are now available. These fix a security issue with severity "low". 5.1.3 also provides a number of additional bugfixes.

For full details, please see the release notes and security advisory:
https://docs.wagtail.org/en/stable/releases/5.1.3.html
GHSA-fc75-58r8-rm3h