Bump dependencies (#874)

* fix pytest-asynio bump to 0.19

* bump mypy

* fix coverage of async fixtures

tests/test_relations/test_cascades.py

@@ -2,6 +2,7 @@ from typing import Optional
 
 import databases
 import pytest
+import pytest_asyncio
 import sqlalchemy
 
 import ormar
@@ -72,7 +73,7 @@ def create_test_database():
     metadata.drop_all(engine)
 
 
-@pytest.fixture(scope="function")
+@pytest_asyncio.fixture(scope="function")
 async def cleanup():
     yield
     async with database: