Update //third_party/protobuf to version 3.

third_party/protobuf/objectivec/google/protobuf/Empty.pbobjc.h

+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: google/protobuf/empty.proto
+
+#import "GPBProtocolBuffers.h"
+
+#if GOOGLE_PROTOBUF_OBJC_GEN_VERSION != 30000
+#error This file was generated by a different version of protoc which is incompatible with your Protocol Buffer library sources.
+#endif
+
+// @@protoc_insertion_point(imports)
+
+CF_EXTERN_C_BEGIN
+
+NS_ASSUME_NONNULL_BEGIN
+
+#pragma mark - GPBEmptyRoot
+
+@interface GPBEmptyRoot : GPBRootObject
+
+// The base class provides:
+//   + (GPBExtensionRegistry *)extensionRegistry;
+// which is an GPBExtensionRegistry that includes all the extensions defined by
+// this file and all files that it depends on.
+
+@end
+
+#pragma mark - GPBEmpty
+
+// A generic empty message that you can re-use to avoid defining duplicated
+// empty messages in your APIs. A typical example is to use it as the request
+// or the response type of an API method. For instance:
+//
+//     service Foo {
+//       rpc Bar(google.protobuf.Empty) returns (google.protobuf.Empty);
+//     }
+//
+// The JSON representation for `Empty` is empty JSON object `{}`.
+@interface GPBEmpty : GPBMessage
+
+@end
+
+NS_ASSUME_NONNULL_END
+
+CF_EXTERN_C_END
+
+// @@protoc_insertion_point(global_scope)