Revert "third_party/protobuf: Update to HEAD (83d681ee2c)"

third_party/protobuf/objectivec/Tests/unittest_extension_chain_g.proto

Index: third_party/protobuf/objectivec/Tests/unittest_extension_chain_g.proto
diff --git a/third_party/protobuf/objectivec/Tests/unittest_extension_chain_g.proto b/third_party/protobuf/objectivec/Tests/unittest_extension_chain_g.proto
deleted file mode 100644
index aee827b176dc0a8dddafa40ead90aa94a0e6093f..0000000000000000000000000000000000000000
--- a/third_party/protobuf/objectivec/Tests/unittest_extension_chain_g.proto
+++ /dev/null
@@ -1,41 +0,0 @@
-// Protocol Buffers - Google's data interchange format
-// Copyright 2016 Google Inc.  All rights reserved.
-//
-// Redistribution and use in source and binary forms, with or without
-// modification, are permitted provided that the following conditions are
-// met:
-//
-//     * Redistributions of source code must retain the above copyright
-// notice, this list of conditions and the following disclaimer.
-//     * Redistributions in binary form must reproduce the above
-// copyright notice, this list of conditions and the following disclaimer
-// in the documentation and/or other materials provided with the
-// distribution.
-//     * Neither the name of Google Inc. nor the names of its
-// contributors may be used to endorse or promote products derived from
-// this software without specific prior written permission.
-//
-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-syntax = "proto2";
-
-package protobuf_unittest;
-
-import "unittest_extension_chain_c.proto";
-
-// The Root for this file should just be merging in the extensions from C's
-// Root.
-
-message ChainGMessage {
-  optional ChainCMessage c = 1;
-}