ci(starlette): Drop direct anyio dependency (#7724)

There is no import of `anyio` in `test_starlette.py` and the pin leads to unsatisfiable constraints.

Closes #7778

Author: alexander-alderman-webb

scripts/populate_tox/config.py

@@ -498,7 +498,6 @@
                 "pytest-asyncio",
                 "python-multipart",
                 "requests",
-                "anyio<4.0.0",
                 "jinja2",
                 "httpx",
             ],