Comment out protobuf_java

This way we can still build //... on machines without a bazel-compatible
Java installation.

Change-Id: I91922671155584aa1fe3223d7b84c757e82166d0
diff --git a/third_party/protobuf/BUILD b/third_party/protobuf/BUILD
index 619bbee..5cad921 100644
--- a/third_party/protobuf/BUILD
+++ b/third_party/protobuf/BUILD
@@ -502,6 +502,7 @@
     tools = [":protoc"],
 )
 
+"""
 java_library(
     name = "protobuf_java",
     srcs = glob([
@@ -511,6 +512,7 @@
     ],
     visibility = ["//visibility:public"],
 )
+"""
 
 ################################################################################
 # Python support