Update WORKSPACE to remove hack protobuf_bzl (#65)

mixerclient/WORKSPACE

@@ -14,17 +14,6 @@
 
 # A Bazel (http://bazel.io) workspace for Istio Mixer client
 
-# Workaround for Bazel > 0.4.0 since it needs newer protobuf.bzl from:
-# https://github.com/google/protobuf/pull/2246
-# Do not use this git_repository for anything else than protobuf.bzl
-new_git_repository(
-    name = "protobuf_bzl",
-    # Injecting an empty BUILD file to prevent using any build target
-    build_file_content = "",
-    commit = "05090726144b6e632c50f47720ff51049bfcbef6",
-    remote = "https://github.com/google/protobuf.git",
-)
-
 load(
     "//:repositories.bzl",
     "boringssl_repositories",
@@ -40,5 +29,5 @@ protobuf_repositories()
 googletest_repositories()
 googleapis_repositories()
 grpc_repositories()
-mixerapi_repositories(protobuf_repo="@protobuf_bzl//")
+mixerapi_repositories()