build(deps): bump idna from 3.7 to 3.15

Bumps [idna](https://github.com/kjd/idna) from 3.7 to 3.15.
- [Release notes](https://github.com/kjd/idna/releases)
- [Changelog](https://github.com/kjd/idna/blob/master/HISTORY.md)
- [Commits](kjd/idna@v3.7...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

@@ -31,7 +31,7 @@ gunicorn==23.0.0
 gitpython==3.1.50
 httplib2==0.19.0
 hvac==0.10.5
-idna==3.7
+idna==3.15
 influxdb==5.3.1
 ipaddress==1.0.23
 ipython-genutils==0.2.0