Upgrade JGit to 4.9.8.201812241815-r

To match the version used in Gerrit since 2.15.8.

Change-Id: I0df16a1efda2473f9aa049cb1c5c5394d104f702
diff --git a/external_plugin_deps.bzl b/external_plugin_deps.bzl
index 5da0bd1..f82ba8c 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:4.7.7.201812240805-r",
-        sha1 = "d2358e838084d2482d51b51b70fd34a356495925",
+            "org.eclipse.jgit:org.eclipse.jgit:4.9.8.201812241815-r",
+        sha1 = "dedb5d05a952551dc465611ebde3819d86bb22fc",
     )
 
     maven_jar(