Fix spelling.

Bug: None
Change-Id: Id281fe3d58bd5a8651b299b426353524085dd876
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/167536
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Rikard Lundmark <lundmark@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30402}

Author: Rikard Lundmark

modules/pacing/pacing_controller.h

@@ -36,7 +36,7 @@
 
 namespace webrtc {
 
-// This class implements a leaky-buck packet pacing algorithm. It handles the
+// This class implements a leaky-bucket packet pacing algorithm. It handles the
 // logic of determining which packets to send when, but the actual timing of
 // the processing is done externally (e.g. PacedSender). Furthermore, the
 // forwarding of packets when they are ready to be sent is also handled