chore(deps): bump idna from 3.4 to 3.15 in /tools/python

Bumps [idna](https://github.com/kjd/idna) from 3.4 to 3.15.
- [Release notes](https://github.com/kjd/idna/releases)
- [Changelog](https://github.com/kjd/idna/blob/master/HISTORY.md)
- [Commits](kjd/idna@v3.4...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]

tools/python/requirements.txt

@@ -12,7 +12,7 @@ grpc-google-iam-v1==0.12.6
 grpcio==1.54.0
 grpcio-status==1.54.0
 httplib2==0.22.0
-idna==3.4
+idna==3.15
 proto-plus==1.22.2
 protobuf==4.22.3
 pyasn1==0.4.8