Remove longboard sample from xcode workspace.

gameplay.xcworkspace/contents.xcworkspacedata

@@ -10,9 +10,6 @@
    <FileRef
       location = "group:samples/character/sample-character.xcodeproj">
    </FileRef>
-   <FileRef
-      location = "group:samples/longboard/sample-longboard.xcodeproj">
-   </FileRef>
    <FileRef
       location = "group:samples/lua/sample-lua.xcodeproj">
    </FileRef>