Update urllib3 requirement from <2 to <3 in /echo-service

Updates the requirements on [urllib3](https://github.com/urllib3/urllib3) to permit the latest version.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/main/CHANGES.rst)
- [Commits](urllib3/urllib3@0.3...2.2.1)

---
updated-dependencies:
- dependency-name: urllib3
  dependency-type: direct:production
...

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

echo-service/requirements.txt

@@ -6,4 +6,4 @@ drf-haystack<1.9
 idna==2.8
 pytz==2018.9
 requests<3
-urllib3<2
+urllib3<3