You have the option of hiding all legends texts associated with the chart or hiding the legend associated with a particular chart.
Hiding all legends texts
Start by clicking on the legend area. Go to the Presentation properties tab in the “Content” group, untick the checkbox “Show legend”.
To bring the legend back into your chart, click below the x-axis, go to the Presentation properties tab, in the “Charts elements” group, tick the “Show legend” checkbox.
Hiding a particular legend text
Click on the graph of the series for which you want to remove the legend text. Go to the Presentation properties tab, in the “Content” group set “Graph text” to “Hidden”.