rm pod downloads badge, they no longer available

Author: jkasten2

README.md

@@ -3,7 +3,7 @@
 </p>
 
 ### OneSignal iOS SDK
-[![CocoaPods](https://img.shields.io/cocoapods/v/OneSignal.svg)](https://cocoapods.org/pods/OneSignal) [![CocoaPods](https://img.shields.io/cocoapods/dm/OneSignal.svg)](https://cocoapods.org/pods/OneSignal) [![Carthage compatible](https://img.shields.io/badge/Carthage-compatible-4BC51D.svg)](https://github.com/Carthage/Carthage) [![SwiftPM Compatible](https://img.shields.io/badge/SwiftPM-Compatible-brightgreen.svg)](https://goo.gl/E01ufX) [![Build Status](https://travis-ci.org/OneSignal/OneSignal-iOS-SDK.svg?branch=master)](https://travis-ci.org/OneSignal/OneSignal-iOS-SDK)
+[![CocoaPods](https://img.shields.io/cocoapods/v/OneSignal.svg)](https://cocoapods.org/pods/OneSignal) [![Carthage compatible](https://img.shields.io/badge/Carthage-compatible-4BC51D.svg)](https://github.com/Carthage/Carthage) [![SwiftPM Compatible](https://img.shields.io/badge/SwiftPM-Compatible-brightgreen.svg)](https://goo.gl/E01ufX) [![Build Status](https://travis-ci.org/OneSignal/OneSignal-iOS-SDK.svg?branch=master)](https://travis-ci.org/OneSignal/OneSignal-iOS-SDK)
 
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