Update required httpx version for v0.23

Author: aiudirog

setup.cfg

@@ -25,7 +25,7 @@ include_package_data = True
 python_requires = >=3.6
 packages = httpx_gssapi
 install_requires =
-    httpx>=0.16,<0.23
+    httpx>=0.16,<0.24
     gssapi
 
 [options.extras_require]