Updating RTCDeviceType with new iOS devices.

Bug: None
Change-Id: I2b5416fda608039c07037244ce69c299f155ffdc
Reviewed-on: https://webrtc-review.googlesource.com/6900
Reviewed-by: Daniela Jovanoska Petrenko <denicija@webrtc.org>
Commit-Queue: Kári Helgason <kthelgason@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20238}

sdk/objc/Framework/Headers/WebRTC/UIDevice+RTCDevice.h

@@ -28,6 +28,11 @@ typedef NS_ENUM(NSInteger, RTCDeviceType) {
   RTCDeviceTypeIPhone6,
   RTCDeviceTypeIPhone6S,
   RTCDeviceTypeIPhone6SPlus,
+  RTCDeviceTypeIPhone7,
+  RTCDeviceTypeIPhone7Plus,
+  RTCDeviceTypeIPhone8,
+  RTCDeviceTypeIPhone8Plus,
+  RTCDeviceTypeIPhoneX,
   RTCDeviceTypeIPodTouch1G,
   RTCDeviceTypeIPodTouch2G,
   RTCDeviceTypeIPodTouch3G,
@@ -58,7 +63,6 @@ typedef NS_ENUM(NSInteger, RTCDeviceType) {
 @interface UIDevice (RTCDevice)
 
 + (RTCDeviceType)deviceType;
-+ (NSString *)stringForDeviceType:(RTCDeviceType)deviceType;
 + (BOOL)isIOS9OrLater;
 + (BOOL)isIOS11OrLater;