Bump idna from 2.10 to 3.7

Bumps [idna](https://github.com/kjd/idna) from 2.10 to 3.7.
- [Release notes](https://github.com/kjd/idna/releases)
- [Changelog](https://github.com/kjd/idna/blob/master/HISTORY.rst)
- [Commits](kjd/idna@v2.10...v3.7)

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

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

requirements.txt

@@ -12,7 +12,7 @@ django-imagekit==4.0.2
 djangorestframework==3.11.2
 et-xmlfile==1.0.1
 flake8==3.9.1
-idna==2.10
+idna==3.7
 jdcal==1.4.1
 mccabe==0.6.1
 oauthlib==3.1.0