fix: Remove non-existent pytest-anyio dependency

The pytest-anyio package doesn't exist on PyPI. The anyio library includes
its own pytest plugin that should be loaded instead.

Changes:
- Remove pytest-anyio>=0.8.0 from dev dependencies
- Add -p anyio to pytest addopts to load anyio's built-in pytest plugin
- Keep trio>=0.20.0 and anyio_backends configuration for multi-backend testing

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: codebydivine

pyproject.toml

@@ -37,7 +37,6 @@ dev = [
     "pytest>=8.0",
     "pytest-cov>=4.0",
     "pytest-asyncio>=0.21",
-    "pytest-anyio>=0.8.0",
     "trio>=0.20.0",
     "python-dotenv>=1.0.0",
     "pre-commit>=3.5.0",
@@ -55,7 +54,8 @@ where = ["src"]
 [tool.pytest.ini_options]
 pythonpath = ["src"]
 testpaths = ["tests"]
-addopts = "--cov=thegraph_token_api --cov-report term-missing"
+addopts = "--cov=thegraph_token_api --cov-report term-missing -p anyio"
+asyncio_mode = "auto"
 anyio_backends = ["asyncio", "trio"]
 
 [tool.coverage.run]