fix: correct pytest async plugin dependency

- Changed pytest-anyio to anyio (the correct package name)
- The anyio package includes built-in pytest plugin support
- pytest-anyio==0.0.0 was causing dependency resolution failures
- anyio>=4.0 provides the pytest plugin for async test support

pyproject.toml

@@ -61,7 +61,7 @@ dev = [
 test = [
     "pytest>=8.3.0",  # Minimum version for Python 3.13 support
 "pytest-timeout>=2.3",
-"pytest-anyio>=4.0",  # For async test support with Python 3.13
+"anyio>=4.0",  # For async test support (includes pytest plugin)
     "llama-index-core>=0.12.0",
     "llama-index-readers-file>=0.4.0",
     "python-dotenv>=1.0.0",