Revert "Enable LEB128 OBU size fields by default."

This reverts commit 4224fa4a6d43afc175fecfab3b32eeb8eec811b6.

It was causing nightly test run failures. Temporarily revert 
to allow time for investigation and fix.

BUG=aomedia:1439

Change-Id: Id3e8dee5f2b744244f6389ee0f93775ff3eed387

build/cmake/aom_config_defaults.cmake

diff --git a/build/cmake/aom_config_defaults.cmake b/build/cmake/aom_config_defaults.cmake
index 15e3c46..910a7b6 100644
--- a/build/cmake/aom_config_defaults.cmake
+++ b/build/cmake/aom_config_defaults.cmake
@@ -131,7 +131,7 @@
 set(CONFIG_MONO_VIDEO 1 CACHE NUMBER "AV1 experiment flag.")
 set(CONFIG_NO_FRAME_CONTEXT_SIGNALING 0 CACHE NUMBER "AV1 experiment flag.")
 set(CONFIG_OBU_NO_IVF 0 CACHE NUMBER "AV1 experiment flag.")
-set(CONFIG_OBU_SIZING 1 CACHE NUMBER "AV1 experiment flag.")
+set(CONFIG_OBU_SIZING 0 CACHE NUMBER "AV1 experiment flag.")
 set(CONFIG_OPT_REF_MV 1 CACHE NUMBER "AV1 experiment flag.")
 set(CONFIG_PALETTE_THROUGHPUT 1 CACHE NUMBER "AV1 experiment flag.")
 set(CONFIG_Q_ADAPT_PROBS 1 CACHE NUMBER "AV1 experiment flag.")