Fix jupyter example on README.md

Author: Mauro Fr

README.md

@@ -191,7 +191,7 @@ The feature `evcxr` should be enabled when including Plotters to Jupyter Noteboo
 The following code shows a minimal example of this.
 
 ```text
-:dep plotters = { git = "https://github.com/38/plotters", default_features = false, features = ["evcxr"] }
+:dep plotters = { git = "https://github.com/38/plotters", default_features = false, features = ["evcxr", "line_series"] }
 extern crate plotters;
 use plotters::prelude::*;