Fix README async example: cursor() is sync, not async

AsyncConnection.cursor() is intentionally sync (for SQLAlchemy
compatibility). Remove the incorrect `await` from the example.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: antoineleclair

README.md

@@ -28,7 +28,7 @@ from dqlitedbapi.aio import aconnect
 
 async def main():
     conn = await aconnect("localhost:9001")
-    cursor = await conn.cursor()
+    cursor = conn.cursor()
     await cursor.execute("SELECT 1")
     print(await cursor.fetchone())
     await conn.close()