Bump python-decouple from 3.4 to 3.8

Bumps [python-decouple](https://github.com/henriquebastos/python-decouple) from 3.4 to 3.8.
- [Release notes](https://github.com/henriquebastos/python-decouple/releases)
- [Changelog](https://github.com/HBNetwork/python-decouple/blob/master/CHANGELOG.md)
- [Commits](HBNetwork/python-decouple@v3.4...v3.8)

---
updated-dependencies:
- dependency-name: python-decouple
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

base-requirements.txt

@@ -11,7 +11,7 @@ cmarkgfm==0.6.0
 Pillow==10.4.0
 psycopg2-binary==2.9.9
 python3-openid==3.2.0
-python-decouple==3.4
+python-decouple==3.8
 # lxml used by BeautifulSoup.
 lxml==5.2.2
 cssselect==1.1.0