Fixed incorrect spelling in pie dataset options. (#6466)

Fixes #6465.

Author: SeppPenner

docs/charts/doughnut.md

@@ -51,7 +51,7 @@ var myDoughnutChart = new Chart(ctx, {
 
 ## Dataset Properties
 
-The doughnut/pie chart allows a number of properties to be specified for each dataset. These are used to set display properties for a specific dataset. For example, the colour of a the dataset's arc are generally set this way.
+The doughnut/pie chart allows a number of properties to be specified for each dataset. These are used to set display properties for a specific dataset. For example, the colours of the dataset's arcs are generally set this way.
 
 | Name | Type | [Scriptable](../general/options.md#scriptable-options) | [Indexable](../general/options.md#indexable-options) | Default
 | ---- | ---- | :----: | :----: | ----