Bump TensorFlow version to pick up necessary changes.
diff --git a/third_party/tensorflow b/third_party/tensorflow
index a489378..c022862 160000
--- a/third_party/tensorflow
+++ b/third_party/tensorflow
@@ -1 +1 @@
-Subproject commit a4893783de1bb62dff22147ad1acd741cc2c08b7
+Subproject commit c0228623425b7eb387f11d5aa82f47199d7be385