[rtp_rtcp] fixed lint errors in rtp_rtcp module that are not fixed in other CLs

webrtc/modules/rtp_rtcp/source/rtcp_format_remb_unittest.cc

Index: webrtc/modules/rtp_rtcp/source/rtcp_format_remb_unittest.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtcp_format_remb_unittest.cc b/webrtc/modules/rtp_rtcp/source/rtcp_format_remb_unittest.cc
index a639f7f7f572940c1d2f1782decffe9108b1a51b..87c0259b3e9f877b03d8158e94dbdf838c173b2e 100644
--- a/webrtc/modules/rtp_rtcp/source/rtcp_format_remb_unittest.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtcp_format_remb_unittest.cc
@@ -26,7 +26,8 @@ namespace {
 
 class TestTransport : public Transport {
  public:
-  TestTransport(RTCPReceiver* rtcp_receiver) : rtcp_receiver_(rtcp_receiver) {}
+  explicit TestTransport(RTCPReceiver* rtcp_receiver)
+      : rtcp_receiver_(rtcp_receiver) {}
 
   bool SendRtp(const uint8_t* /*data*/,
                size_t /*len*/,