Fix a typo

docs/fastapi.md

@@ -58,7 +58,7 @@ async def shutdown() -> None:
 
 Define ormar models with appropriate fields. 
 
-Those models will be used insted of pydantic ones.
+Those models will be used instead of pydantic ones.
 
 ```python
 class Category(ormar.Model):
@@ -210,4 +210,4 @@ def test_all_endpoints():
 [fastapi]: https://fastapi.tiangolo.com/
 [models]: ./models/index.md
 [database initialization]:  ./models/migrations.md
-[tests]: https://github.com/collerek/ormar/tree/master/tests
+[tests]: https://github.com/collerek/ormar/tree/master/tests