docs minor fix

Author: pdina

docs/src/piccolo/engines/postgres_engine.rst

@@ -37,7 +37,7 @@ pool in the shutdown event handler.
 
 .. code-block:: python
 
-    from piccolo.engine import from starlette.applications import Starlette
+    from piccolo.engine import engine_finder
     from starlette.applications import Starlette