[deps] Update pillow requirement from ~=11.3.0 to ~=12.0.0

Updates the requirements on [pillow](https://github.com/python-pillow/Pillow) to permit the latest version.
- [Release notes](https://github.com/python-pillow/Pillow/releases)
- [Changelog](https://github.com/python-pillow/Pillow/blob/main/CHANGES.rst)
- [Commits](python-pillow/Pillow@11.3.0...12.0.0)

---
updated-dependencies:
- dependency-name: pillow
  dependency-version: 12.0.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

requirements.txt

@@ -1,5 +1,5 @@
 django>=4.2.0,<5.3.0
 django-leaflet~=0.33.0
-Pillow~=11.3.0
+Pillow~=12.0.0
 geopy~=2.4.1
 openwisp-utils[channels] @ https://github.com/openwisp/openwisp-utils/archive/refs/heads/1.3.tar.gz