Disable EndToEndTest.AssignsTrans... for memcheck

The test is flaky on the bot.

BUG=webrtc:5134
TBR=sprang@webrtc.org
NOTRY=true

Review URL: https://codereview.webrtc.org/1406063006

Cr-Commit-Position: refs/heads/master@{#10436}
diff --git a/tools/valgrind-webrtc/gtest_exclude/video_engine_tests.gtest-memcheck.txt b/tools/valgrind-webrtc/gtest_exclude/video_engine_tests.gtest-memcheck.txt
index 6e4392f..57387dc 100644
--- a/tools/valgrind-webrtc/gtest_exclude/video_engine_tests.gtest-memcheck.txt
+++ b/tools/valgrind-webrtc/gtest_exclude/video_engine_tests.gtest-memcheck.txt
@@ -3,3 +3,6 @@
 EndToEndTest.SendsAndReceivesVP9
 EndToEndTest.RestartingSendStreamPreservesRtpStatesWithRtx
 VideoSendStreamTest.VP9FlexMode
+
+# Flaky under memcheck (WebRTC issue 5134)
+EndToEndTest.AssignsTransportSequenceNumbers