sctp: Rename SctpTransport to UsrSctpTransport

The rename ensures we don't confuse this implementation with
the new one based on the new dcSCTP library.

Bug: webrtc:12614
No-Presubmit: True
Change-Id: Ida08659bbea9c98aba8247d4368799ff7dd18729
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/214482
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Florent Castelli <orphis@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33688}
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index 6149683..e475f22 100755
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -21,7 +21,7 @@
     'examples/objc',
     'media/base/stream_params.h',
     'media/base/video_common.h',
-    'media/sctp/sctp_transport.cc',
+    'media/sctp/usrsctp_transport.cc',
     'modules/audio_coding',
     'modules/audio_device',
     'modules/audio_processing',