Bump idna from 3.6 to 3.7 in /server (#34)

Bumps [idna](https://github.com/kjd/idna) from 3.6 to 3.7.
- [Release notes](https://github.com/kjd/idna/releases)
- [Changelog](https://github.com/kjd/idna/blob/master/HISTORY.rst)
- [Commits](kjd/idna@v3.6...v3.7)

---
updated-dependencies:
- dependency-name: idna
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

server/requirements.txt

@@ -174,7 +174,7 @@ httplib2==0.22.0
     # via oauth2client
 icalendar==4.0.9
     # via superdesk-planning
-idna==3.6
+idna==3.7
     # via
     #   email-validator
     #   requests