[deps] Update tldextract requirement in /images/openwisp_base

Updates the requirements on [tldextract](https://github.com/john-kurkowski/tldextract) to permit the latest version.
- [Release notes](https://github.com/john-kurkowski/tldextract/releases)
- [Changelog](https://github.com/john-kurkowski/tldextract/blob/master/CHANGELOG.md)
- [Commits](john-kurkowski/tldextract@5.1.2...5.1.3)

---
updated-dependencies:
- dependency-name: tldextract
  dependency-type: direct:production
...

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

images/openwisp_base/requirements.txt

@@ -8,7 +8,7 @@ django-cors-headers~=4.6
 django-pipeline~=3.1
 uwsgi~=2.0.28
 django-celery-email~=3.0.0
-tldextract~=5.1.2
+tldextract~=5.1.3
 # these add support for object storage
 # (eg: Amazon S3, GCS)
 django-storages~=1.14.4