Bump global-refdb to v3.4.8.6

Change-Id: I368adb357210698eaed9130568f4d6ad240e1b79

external_plugin_deps.bzl

diff --git a/external_plugin_deps.bzl b/external_plugin_deps.bzl
index aed23bd..67807c2 100644
--- a/external_plugin_deps.bzl
+++ b/external_plugin_deps.bzl
@@ -79,6 +79,6 @@
 
     maven_jar(
         name = "global-refdb",
-        artifact = "com.gerritforge:global-refdb:3.3.2.1",
-        sha1 = "00b6b0f39b3c8fc280a19d91fb0681954ebccd02",
+        artifact = "com.gerritforge:global-refdb:3.4.8.6",
+        sha1 = "5b8e943f94c64e3164e0d78f1c27795db7f72a4f",
     )