Reduce number of tests for DatarateTest

BUG=aomedia:506

Change-Id: I8b52eadefa1946c082bdd06f07657aa2d43e3f2c

test/datarate_test.cc

@@ -249,5 +249,5 @@ TEST_P(DatarateTestLarge, ChangingDropFrameThresh) {
 AV1_INSTANTIATE_TEST_CASE(DatarateTestLarge,
                           ::testing::Values(::libaom_test::kOnePassGood,
                                             ::libaom_test::kRealTime),
-                          ::testing::Range(2, 9, 2));
+                          ::testing::Values(2, 5));
 }  // namespace