test_http2_via_proxy failure on unexpected keyword argument

[nieder]

Describe the bug
building proxy.py with python3.10 on macOS, I get this test failure:

/sw/bin/python3.10 -m pytest -vv || exit 2
==================================================================================================== test session starts =====================================================================================================
platform darwin -- Python 3.10.4, pytest-7.4.4, pluggy-1.4.0 -- /sw/bin/python3.10
cachedir: .pytest_cache
rootdir: /sw/build.build/proxy.py-py310-2.4.10-1/proxy_py-2.4.10
configfile: pytest.ini
testpaths: tests/
plugins: cov-6.0.0, anyio-0.0.0, asyncio-0.21.1, mock-3.12.0, xdist-3.5.0
asyncio: mode=strict
collected 247 items                                                                                                                                                                                                          
...
tests/http/parser/test_tls_parser.py::TestTlsParser::test_parse_server_hello PASSED                                                                                                                [ 73%]
tests/http/proxy/test_http2.py::TestHttp2WithProxy::test_http2_via_proxy FAILED                                                                                                                    [ 74%]
tests/http/proxy/test_http_proxy.py::TestHttpProxyPlugin::test_proxy_plugin_not_initialized_unless_first_request_completes PASSED                                                                  [ 74%]
...
__________________________________________________________________________________________ TestHttp2WithProxy.test_http2_via_proxy ___________________________________________________________________________________________

self = <tests.http.proxy.test_http2.TestHttp2WithProxy testMethod=test_http2_via_proxy>

    def test_http2_via_proxy(self) -> None:
        assert self.PROXY
        proxy_url = 'http://localhost:%d' % self.PROXY.flags.port
        proxies: Dict[str, Any] = (
            {
                'proxies': {
                    'all://': proxy_url,
                },
            }
            # For Python>=3.11, proxies keyword is deprecated by httpx
            if sys.version_info < (3, 7, 0)
            else {'proxy': proxy_url}
        )
        response = httpx.get(
            'https://www.google.com',
            headers={'accept': 'application/json'},
>           verify=httpx.create_ssl_context(http2=True),
            timeout=httpx.Timeout(timeout=5.0),
            **proxies,
        )
E       TypeError: create_ssl_context() got an unexpected keyword argument 'http2'

proxies    = {'proxy': 'http://localhost:56231'}
proxy_url  = 'http://localhost:56231'
self       = <tests.http.proxy.test_http2.TestHttp2WithProxy testMethod=test_http2_via_proxy>

To Reproduce
Run proxy.py tests with python3.10 -m pytest

Expected behavior
The tests run and all should pass.

Version information

• OS: macOS 10.14.6
• Browser Firefox, but not applicable
• Device: iMac
• proxy.py Version 2.4.10

Additional context
httpx-0.28.1 is installed