Fix NSInteger formatting warning from clang 6

webrtc/sdk/objc/Framework/Classes/PeerConnection/RTCCameraVideoCapturer.m

Index: webrtc/sdk/objc/Framework/Classes/PeerConnection/RTCCameraVideoCapturer.m
diff --git a/webrtc/sdk/objc/Framework/Classes/PeerConnection/RTCCameraVideoCapturer.m b/webrtc/sdk/objc/Framework/Classes/PeerConnection/RTCCameraVideoCapturer.m
index a2290c2458405a1d39458f64eae820abfdc14bc9..488a7e34894924b7c4d0d5ecf95f494846794635 100644
--- a/webrtc/sdk/objc/Framework/Classes/PeerConnection/RTCCameraVideoCapturer.m
+++ b/webrtc/sdk/objc/Framework/Classes/PeerConnection/RTCCameraVideoCapturer.m
@@ -121,7 +121,7 @@ static inline BOOL IsMediaSubTypeSupported(FourCharCode mediaSubType) {
   [RTCDispatcher
       dispatchAsyncOnType:RTCDispatcherTypeCaptureSession
                     block:^{
-                      RTCLogInfo("startCaptureWithDevice %@ @ %zd fps", format, fps);
+                      RTCLogInfo("startCaptureWithDevice %@ @ %ld fps", format, (long)fps);
 
 #if TARGET_OS_IPHONE
                       [[UIDevice currentDevice] beginGeneratingDeviceOrientationNotifications];