Revert "Disable AV1/AVxEncoderThreadRTTest for speed 9"

This reverts commit d029bcfdaf3c5d77d71f8f61461ce79794a79e01.

Reason for revert:
With the issue reported in BUG=aomedia:2956 fixed, real-time
multi-threading test for speed 9 is enabled.

Change-Id: Ia6795b7d5f1f2362830d48b870f48ed3c9799d13

test/ethread_test.cc

diff --git a/test/ethread_test.cc b/test/ethread_test.cc
index a7669e1..9c7e5d1 100644
--- a/test/ethread_test.cc
+++ b/test/ethread_test.cc
@@ -472,17 +472,10 @@
                            ::testing::Values(0, 2), ::testing::Values(0, 1));
 
 // Test cpu_used 7, 8, 9 here.
-// TODO(chiyotsai@google.com): The test on speed 9 is temporarily disabled due
-// to BUG=aomedia:2956. Re-enable it once it's fixed.
 AV1_INSTANTIATE_TEST_SUITE(AVxEncoderThreadRTTest,
                            ::testing::Values(::libaom_test::kRealTime),
-                           ::testing::Values(7, 8), ::testing::Values(0, 2),
+                           ::testing::Values(7, 8, 9), ::testing::Values(0, 2),
                            ::testing::Values(0, 2), ::testing::Values(0, 1));
-// AV1_INSTANTIATE_TEST_SUITE(AVxEncoderThreadRTTest,
-//                            ::testing::Values(::libaom_test::kRealTime),
-//                            ::testing::Values(7, 8, 9), ::testing::Values(0,
-//                            2),
-//                            ::testing::Values(0, 2), ::testing::Values(0, 1));
 
 // Test cpu_used 0, 1, 3 and 5.
 AV1_INSTANTIATE_TEST_SUITE(AVxEncoderThreadTestLarge,