message: video frame: fix grammar
  Cr-Commit-Position: refs/heads/master@{#33190}
diff: @@ -134,11 +134,11 @@ class RTC_EXPORT VideoFrame {
  // Get frame size in pixels.
  uint32_t size() const;
  - // Get frame ID. Returns 0 if ID is not set. Not guarantee to be transferred
  - // from the sender to the receiver, but preserved on single side. The id
  + // Get frame ID. Returns 0 if ID is not set. Not guaranteed to be transferred
  + // from the sender to the receiver, but preserved on the sender side. The id
  // should be propagated between all frame modifications during its lifetime
  // from capturing to sending as encoded image. It is intended to be unique
  - // over a time window of a few minutes for peer connection, to which
  + // over a time window of a few minutes for the peer connection to which the
  // corresponding video stream belongs to.
  uint16_t id() const { return id_; }
  void set_id(uint16_t id) { id_ = id; }
  