Don't use the official manifest on stabilize-5116.88.B.

This branch has a working regular manifest, but the official
manifest is not set up yet, nor needed. Switch over.

BUG=none
TEST=cbuildbot_config_unittest.py

Change-Id: I70308afd63f14e0eee770e57ea31dddcb0e83a46
Previous-Reviewed-on: https://chromium-review.googlesource.com/188647
(cherry picked from commit 0488c04afba00f369c3b04604abab6a216593397)
Reviewed-on: https://chromium-review.googlesource.com/189615
Reviewed-by: Dharani Govindan <dharani@chromium.org>
Tested-by: Dharani Govindan <dharani@chromium.org>
diff --git a/buildbot/cbuildbot_config.py b/buildbot/cbuildbot_config.py
index c3cf9ba..7748813 100755
--- a/buildbot/cbuildbot_config.py
+++ b/buildbot/cbuildbot_config.py
@@ -1566,7 +1566,6 @@
   build_type=constants.CANARY_TYPE,
   useflags=official['useflags'] + ['-cros-debug', '-highdpi'],
   build_tests=True,
-  manifest=constants.OFFICIAL_MANIFEST,
   manifest_version=True,
   images=['base', 'test', 'factory_test', 'factory_install'],
   push_image=True,