upgrade ubsan RBE toolchain
diff --git a/tools/remote_build/rbe_common.bazelrc b/tools/remote_build/rbe_common.bazelrc
index 568e7ae..530ad2d 100644
--- a/tools/remote_build/rbe_common.bazelrc
+++ b/tools/remote_build/rbe_common.bazelrc
@@ -92,4 +92,4 @@
 # how to update the bazel toolchain for ubsan:
 # - check for the latest released version in https://github.com/bazelbuild/bazel-toolchains/tree/master/configs/experimental/ubuntu16_04_clang
 # - you might need to update the bazel_toolchains dependency in grpc_deps.bzl
-build:ubsan --crosstool_top=@bazel_toolchains//configs/experimental/ubuntu16_04_clang/1.2/bazel_0.28.0/ubsan:toolchain
+build:ubsan --crosstool_top=@bazel_toolchains//configs/experimental/ubuntu16_04_clang/1.3/bazel_0.29.1/ubsan:toolchain