Bump idna from 3.7 to 3.15 in /tfx/tools/docker

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]

tfx/tools/docker/requirements.txt

@@ -128,7 +128,7 @@ httpcore==1.0.9
 httplib2==0.22.0
 httpx==0.28.1
 identify==2.6.1
-idna==3.7
+idna==3.15
 importlib_metadata==8.4.0
 importlib_resources==6.4.5
 inflection==0.5.1