Fix spelling mistake in rtp_rtcp.h.

webrtc/modules/rtp_rtcp/include/rtp_rtcp.h

Index: webrtc/modules/rtp_rtcp/include/rtp_rtcp.h
diff --git a/webrtc/modules/rtp_rtcp/include/rtp_rtcp.h b/webrtc/modules/rtp_rtcp/include/rtp_rtcp.h
index bb9e1f2959878b77886e45652e2e0c6eafd60b72..78b89b1a4c97f65375cb267cb0433c8ca4c85920 100644
--- a/webrtc/modules/rtp_rtcp/include/rtp_rtcp.h
+++ b/webrtc/modules/rtp_rtcp/include/rtp_rtcp.h
@@ -118,7 +118,7 @@ class RtpRtcp : public Module {
   // Returns -1 on failure else 0.
   virtual int32_t SetMaxTransferUnit(uint16_t size) = 0;
 
-  // Sets transtport overhead. Default is IPv4 and UDP with no encryption.
+  // Sets transport overhead. Default is IPv4 and UDP with no encryption.
   // |tcp| - true for TCP false UDP.
   // |ipv6| - true for IP version 6 false for version 4.
   // |authentication_overhead| - number of bytes to leave for an authentication