Remove typo (#734)

Author: byBenPuls

README.md

@@ -16,7 +16,7 @@ iex> Postgrex.query!(pid, "SELECT user_id, text FROM comments", [])
 %Postgrex.Result{command: :select, empty?: false, columns: ["user_id", "text"], rows: [[3,"hey"],[4,"there"]], size: 2}}
 
 iex> Postgrex.query!(pid, "INSERT INTO comments (user_id, text) VALUES (10, 'heya')", [])
-%Postgrex.Result{command: :insert, columns: nil, rows: nil, num_rows: 1}}
+%Postgrex.Result{command: :insert, columns: nil, rows: nil, num_rows: 1}
 ```
 
 ## Features