Update selections.md

Author: LiamConnors

Diff for: doc/python/selections.md

@@ -145,7 +145,7 @@ Selections are also supported on time series figures. Here, we add a rectangular
 import plotly.express as px
 
 df = px.data.stocks()
-fig = px.line(df, x='date', y="GOOG")
+fig = px.line(df, x='date', y="GOOG", markers=True)
 fig.add_selection(x0="2019-01-01", y0=0.95, x1="2019-10-01", y1=1.15)
 fig.show()
 ```