dropped Perspex prefix folder from step

docs/build.md

@@ -19,7 +19,7 @@ is linked as a submodule in the git repository, so run:
 
     git submodule update --init
     
-The next step is to download the Skia native libraries. Run ```getnatives.ps1``` PowerShell script which can be found under the folder ```Perspex\src\Skia\```.
+The next step is to download the Skia native libraries. Run ```getnatives.ps1``` PowerShell script which can be found under the folder ```src\Skia\```.
 
 ## Linux