Update axes.md

Author: LiamConnors

doc/python/axes.md

@@ -483,7 +483,7 @@ fig.show()
 
 On date or linear axes, use `ticklabelindex` to draw a label for a minor tick instead of a major tick.
 
-To draw the label for the minor tick before each major tick, set `ticklabelindex` -1, like in the following example.
+To draw the label for the minor tick before each major tick, set `ticklabelindex=-1`, like in the following example.
 
 ```python
 import plotly.express as px