Minor README typo fix
Minor README typo fix

AppHubPlatform/apphub,AppHubPlatform/apphub,AppHubPlatform/apphub,AppHubPlatform/apphub,AppHubPlatform/apphub-ios,AppHubPlatform/apphub-ios,AppHubPlatform/apphub-ios,AppHubPlatform/apphub-ios,AppHubPlatform/apphub-ios,AppHubPlatform/apphub