dering_test: mark TestSpeed disabled

performance characteristics in test environments vary, speed tests
should be for local performance testing. these can still be run with:
--gtest_filter=*TestSpeed* --gtest_also_run_disabled_tests

Change-Id: I4c00ca6970ba7dc8387ee509e695ec922810c3ae

test/dering_test.cc

@@ -246,7 +246,7 @@ TEST_P(DeringDirTest, TestSIMDNoMismatch) {
   test_dering(bsize, 1, dering, ref_dering);
 }
 
-TEST_P(DeringSpeedTest, TestSpeed) {
+TEST_P(DeringSpeedTest, DISABLED_TestSpeed) {
   test_dering_speed(bsize, 4, dering, ref_dering);
 }
 
@@ -254,7 +254,7 @@ TEST_P(DeringFindDirTest, TestSIMDNoMismatch) {
   test_finddir(finddir, ref_finddir);
 }
 
-TEST_P(DeringFindDirSpeedTest, TestSpeed) {
+TEST_P(DeringFindDirSpeedTest, DISABLED_TestSpeed) {
   test_finddir_speed(finddir, ref_finddir);
 }