Bump idna from 2.10 to 3.15

Bumps [idna](https://github.com/kjd/idna) from 2.10 to 3.15.
- [Release notes](https://github.com/kjd/idna/releases)
- [Changelog](https://github.com/kjd/idna/blob/master/HISTORY.md)
- [Commits](kjd/idna@v2.10...v3.15)

---
updated-dependencies:
- dependency-name: idna
  dependency-version: '3.15'
  dependency-type: direct:production
...

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

Author: dependabot[bot]

requirements.txt

@@ -6,7 +6,7 @@ chardet==3.0.4
 Django==3.0.8
 django-cors-headers==3.4.0
 djangorestframework==3.11.0
-idna==2.10
+idna==3.15
 importlib-metadata==1.7.0
 isort==4.3.21
 lazy-object-proxy==1.4.3