Mark Spdy3ConnectionTest#serverSendsSettingsToClient as known failure.

This is the second attempt to submit this CL. The first attempt had a
trailing comma on line 1409, which broke ART build bots.

This test is flaky both on Android Pie and the latest development branch.
I haven't looked too deeply into _why_ it is failing, so it _could_
indicate a serious problem, but since the test on the surface is testing
functionality that isn't used on Android, it might not be worth
investigating. This CL marks the test as a known failure.

Bug: 116289659
Bug: 138134183
Test: art/tools/buildbot-build.sh --host -j100 ; \
      art/tools/run-libcore-tests.sh --mode=host --variant=X32 --debug

Change-Id: Ic0b2f3d9ef8a76bb6e8f55c401cf87a8a806572a
(cherry picked from commit 6023ab703e7a6b4dd685d0ae06af846a3ab66941)
diff --git a/expectations/knownfailures.txt b/expectations/knownfailures.txt
index 1343edc..46221d1 100644
--- a/expectations/knownfailures.txt
+++ b/expectations/knownfailures.txt
@@ -1426,6 +1426,13 @@
   ]
 },
 {
+  description: "OkHttp flaky test of functionality that's not used on Android",
+  bug: 138134183,
+  names: [
+    "com.squareup.okhttp.internal.framed.Spdy3ConnectionTest#serverSendsSettingsToClient"
+  ]
+},
+{
   description: "libcore.java.text.DecimalFormatSymbolsTest#test_getInstance_unknown_or_invalid_locale assumes fallback to locale other than en_US_POSIX.",
   bug: 17422813,
   names: [