[deps] Update django-leaflet requirement from ~=0.30.1 to ~=0.31.0

Updates the requirements on [django-leaflet](https://github.com/makinacorpus/django-leaflet) to permit the latest version.
- [Release notes](https://github.com/makinacorpus/django-leaflet/releases)
- [Changelog](https://github.com/makinacorpus/django-leaflet/blob/master/CHANGES)
- [Commits](makinacorpus/django-leaflet@0.30.1...0.31.0)

---
updated-dependencies:
- dependency-name: django-leaflet
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Federico Capoano <[email protected]>

requirements.txt

@@ -1,7 +1,7 @@
 # Does not supports Django 4.0.0
 django>=3.2.18,!=4.0.*,<4.3
 channels~=3.0.4
-django-leaflet~=0.30.1
+django-leaflet~=0.31.0
 Pillow~=10.4.0
 geopy~=2.4.1
 openwisp-utils~=1.1.0