Upgrade JGit to 5.2.1.201812262042-r

To match the version used on Gerrit's master branch.

Change-Id: I05069550d4a2df233b0c42a0df2799fba03268cf
diff --git a/external_plugin_deps.bzl b/external_plugin_deps.bzl
index 51389e6..d61fcdb 100644
--- a/external_plugin_deps.bzl
+++ b/external_plugin_deps.bzl
@@ -111,8 +111,8 @@
     maven_jar(
         name = "jgit",
         artifact =
-            "org.eclipse.jgit:org.eclipse.jgit:5.1.5.201812261915-r",
-        sha1 = "e64c71932a2a8fdc2b86cf7d5d61c3399c64b8b1",
+            "org.eclipse.jgit:org.eclipse.jgit:5.2.1.201812262042-r",
+        sha1 = "34914e63e1463e40ba40e2e28b0392993ea3b938",
     )
 
     maven_jar(