Update trex_tableau_viz_ref.md

Fix typo

Author: Craigfis

docs/trex_tableau_viz_ref.md

@@ -62,7 +62,7 @@ The following shows an example `inputSpec` that creates a bar chart image.
 ```
 
 ---
-## Descripion of `inputSpec` properties
+## Description of `inputSpec` properties
 
 The following table describes the properties in the `inputSpec`, the JavaScript object that you provide as input to the `createVizImageAsync` method.
 
@@ -303,4 +303,4 @@ For example, you could set a custom palette as shown in the following examples:
 
    palette: tableau.VizImagePaletteType.CustomSequential,  end: "#FFB6C1"
 
-  ```
+  ```