Revert "Upgrade protobuf-java to 3.4.0"

This reverts commit 7786dcc3da859d86757e13ca36ee46c083b088f1.

This should have been done after releasing a version of gitiles
with upgraded JGit that can be used in gerrit 2.15.

Change-Id: Icae01d5b392366381ca05c01aeb86e73f9f440af

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
index d1faf89..1122bcf 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -116,8 +116,8 @@
 
 maven_jar(
     name = "protobuf",
-    artifact = "com.google.protobuf:protobuf-java:3.4.0",
-    sha1 = "b32aba0cbe737a4ca953f71688725972e3ee927c",
+    artifact = "com.google.protobuf:protobuf-java:3.0.0-beta-2",
+    sha1 = "de80fe047052445869b96f6def6baca7182c95af",
 )
 
 maven_jar(