chore: hardcode httpx to less than 0.28.0 for asgi (#14516)

While looking over the riotfile with @brettlangdon , we found that the
httpx library changed how "app" is handled in the newer version so this
pins the httpx version in the asgi version to less than 0.28.0.

It looks like the appsec test already does this in the riotfile:
https://github.com/DataDog/dd-trace-py/blob/01e267e5da4ffcc27b57a8b5148d78af088371fe/riotfile.py#L261

## Checklist
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## Reviewer Checklist
- [ ] Reviewer has checked that all the criteria below are met 
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Author: wantsui

.riot/requirements/10d379e.txt

@@ -0,0 +1,30 @@
+#
+# This file is autogenerated by pip-compile with Python 3.12
+# by the following command:
+#
+#    pip-compile --allow-unsafe --no-annotate .riot/requirements/10d379e.in
+#
+anyio==4.10.0
+asgiref==3.9.1
+attrs==25.3.0
+certifi==2025.8.3
+coverage[toml]==7.10.6
+h11==0.16.0
+httpcore==1.0.9
+httpx==0.27.2
+hypothesis==6.45.0
+idna==3.10
+iniconfig==2.1.0
+mock==5.2.0
+opentracing==2.4.0
+packaging==25.0
+pluggy==1.6.0
+pygments==2.19.2
+pytest==8.4.2
+pytest-asyncio==0.21.1
+pytest-cov==6.2.1
+pytest-mock==3.15.0
+pytest-randomly==3.16.0
+sniffio==1.3.1
+sortedcontainers==2.4.0
+typing-extensions==4.15.0

.riot/requirements/1147178.txt

@@ -2,27 +2,28 @@
 # This file is autogenerated by pip-compile with Python 3.13
 # by the following command:
 #
-#    pip-compile --allow-unsafe --no-annotate .riot/requirements/3b804dc.in
+#    pip-compile --allow-unsafe --no-annotate .riot/requirements/166d447.in
 #
-anyio==4.6.0
-asgiref==3.8.1
-attrs==24.2.0
-certifi==2024.8.30
-coverage[toml]==7.6.1
-h11==0.14.0
-httpcore==1.0.6
+anyio==4.10.0
+asgiref==3.9.1
+attrs==25.3.0
+certifi==2025.8.3
+coverage[toml]==7.10.6
+h11==0.16.0
+httpcore==1.0.9
 httpx==0.27.2
 hypothesis==6.45.0
 idna==3.10
-iniconfig==2.0.0
-mock==5.1.0
+iniconfig==2.1.0
+mock==5.2.0
 opentracing==2.4.0
-packaging==24.1
-pluggy==1.5.0
-pytest==8.3.3
+packaging==25.0
+pluggy==1.6.0
+pygments==2.19.2
+pytest==8.4.2
 pytest-asyncio==0.21.1
-pytest-cov==5.0.0
-pytest-mock==3.14.0
-pytest-randomly==3.15.0
+pytest-cov==6.2.1
+pytest-mock==3.15.0
+pytest-randomly==3.16.0
 sniffio==1.3.1
 sortedcontainers==2.4.0

.riot/requirements/1295cc0.txt

@@ -0,0 +1,34 @@
+#
+# This file is autogenerated by pip-compile with Python 3.8
+# by the following command:
+#
+#    pip-compile --allow-unsafe --no-annotate .riot/requirements/19aeb31.in
+#
+anyio==4.5.2
+asgiref==3.0.0
+async-timeout==3.0.1
+attrs==25.3.0
+certifi==2025.8.3
+coverage[toml]==7.6.1
+exceptiongroup==1.3.0
+h11==0.16.0
+httpcore==1.0.9
+httpx==0.27.2
+hypothesis==6.45.0
+idna==3.10
+importlib-metadata==8.5.0
+iniconfig==2.1.0
+mock==5.2.0
+opentracing==2.4.0
+packaging==25.0
+pluggy==1.5.0
+pytest==8.3.5
+pytest-asyncio==0.21.1
+pytest-cov==5.0.0
+pytest-mock==3.14.1
+pytest-randomly==3.15.0
+sniffio==1.3.1
+sortedcontainers==2.4.0
+tomli==2.2.1
+typing-extensions==4.13.2
+zipp==3.20.2