Upgrade gitiles-servlet to 0.2-4

Change-Id: I149f6bd3eb77e5c3af8847c6a74acbce0a731dda
diff --git a/external_plugin_deps.bzl b/external_plugin_deps.bzl
index d36ce64..47a53eb 100644
--- a/external_plugin_deps.bzl
+++ b/external_plugin_deps.bzl
@@ -5,8 +5,8 @@
 def external_plugin_deps():
   maven_jar(
     name = 'gitiles_servlet',
-    artifact = 'com.google.gitiles:gitiles-servlet:0.2-3',
-    sha1 = 'dfba4b00f748e579797aadb3fd3b2fd5c85c45ed',
+    artifact = 'com.google.gitiles:gitiles-servlet:0.2-4',
+    sha1 = '878a5187a1e7a07ebd9a198cb898f56e6b70c976',
     repository = GERRIT,
   )