update httpx to newer version

Author: wing328

modules/openapi-generator/src/main/resources/python-fastapi/requirements.mustache

@@ -13,7 +13,7 @@ graphql-core==2.3.2
 graphql-relay==2.0.1
 h11==0.16.0
 httptools>=0.3.0,<0.7.0
-httpx==0.24.1
+httpx==0.28.1
 idna==3.7
 itsdangerous==1.1.0
 Jinja2==3.1.4

samples/server/petstore/python-fastapi/requirements.txt

@@ -13,7 +13,7 @@ graphql-core==2.3.2
 graphql-relay==2.0.1
 h11==0.16.0
 httptools>=0.3.0,<0.7.0
-httpx==0.24.1
+httpx==0.28.1
 idna==3.7
 itsdangerous==1.1.0
 Jinja2==3.1.4