Require urllib3 >=2.6.1 to avoid broken 2.6.0 release (#414)

urllib3 2.6.0 removed getheader()/getheaders() from HTTPResponse,
breaking the OpenAPI-generated client. The methods were restored in
2.6.1 three days later. Bump the minimum to skip the broken version.

To remove the deprecated getheader()/getheaders(), we'll need to bump
the version of our generator. This introduced some more issues when I
tried it, so leaving that for another time.

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: f-wright

pyproject.toml

@@ -9,7 +9,7 @@ packages = [
     {include = "**/*.py", from = "src"},
 ]
 readme = "README.md"
-version = "0.23.4"
+version = "0.24.0"
 
 [tool.poetry.dependencies]
 # For certifi, use ">=" instead of "^" since it upgrades its "major version" every year, not really following semver
@@ -21,7 +21,7 @@ python = ">=3.9,<4.0"
 python-dateutil = "^2.9.0"
 requests = "^2.28.2"
 typer = "^0.15.4"
-urllib3 = "^2.5.0"
+urllib3 = "^2.6.1"
 
 [tool.poetry.group.dev.dependencies]
 datamodel-code-generator = "^0.35.0"