Relax restriction on httpx to include 0.28

Author: tsmith023

setup.cfg

@@ -31,7 +31,7 @@ packages =
 platforms = any
 include_package_data = True
 install_requires =
-    httpx>=0.26.0,<0.28.0
+    httpx>=0.26.0,<0.29.0
     validators==0.34.0
     authlib>=1.2.1,<1.3.2
     pydantic>=2.8.0,<3.0.0