Bump idna from 2.8 to 3.7 in /infra/python/deps

Bumps [idna](https://github.com/kjd/idna) from 2.8 to 3.7.
- [Release notes](https://github.com/kjd/idna/releases)
- [Changelog](https://github.com/kjd/idna/blob/master/HISTORY.rst)
- [Commits](https://github.com/kjd/idna/compare/v2.8...v3.7)

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

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

infra/python/deps/requirements.txt

@@ -54,7 +54,7 @@ pywebhdfs == 0.3.2
   pbr == 3.1.1
 requests == 2.21.0
   chardet == 3.0.4
-  idna == 2.8
+  idna == 3.7
   urllib3 == 1.24.2
   certifi == 2020.12.5
 sasl == 0.2.1