Upgrade metrics-jmx to 4.0.3

To match the version of metrics-core used in gerrit since
2.14.11.

Change-Id: I61fab18ad28d3e3302c96ee13ae5dc6345f6bc40
diff --git a/external_plugin_deps.bzl b/external_plugin_deps.bzl
index 2d40d7d..0e99761 100644
--- a/external_plugin_deps.bzl
+++ b/external_plugin_deps.bzl
@@ -3,6 +3,6 @@
 def external_plugin_deps():
     maven_jar(
         name = "metrics_jmx",
-        artifact = "io.dropwizard.metrics:metrics-jmx:4.0.2",
-        sha1 = "c8c14f6d66100a6b79f5d4b6de1d50ccc7f627fb",
+        artifact = "io.dropwizard.metrics:metrics-jmx:4.0.3",
+        sha1 = "d49313634a606496433e34b733251ba9fdbb333f",
     )