build(deps): Bump wagtail from 3.0.3 to 5.1.1

Bumps [wagtail](https://github.com/wagtail/wagtail) from 3.0.3 to 5.1.1.
- [Release notes](https://github.com/wagtail/wagtail/releases)
- [Changelog](https://github.com/wagtail/wagtail/blob/main/CHANGELOG.txt)
- [Commits](wagtail/wagtail@v3.0.3...v5.1.1)

---
updated-dependencies:
- dependency-name: wagtail
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

requirements/base.txt

@@ -43,7 +43,7 @@ django-sass-processor
 pylint-django==2.5.3
 
 # Wagtail
-wagtail==3.0.3
+wagtail==5.1.1
 wagtailmenus==3.1.7 # CANNOT UPDATE
 git+https://github.com/jcmundy/wagtail-autocomplete.git@master#egg=wagtail-autocomplete
 #wagtail-autocomplete==0.3.1