Format external_plugin_deps.bzl with buildifier

Change-Id: I4e73f3f9759126de01bc271ce68b1b84871edb89
diff --git a/external_plugin_deps.bzl b/external_plugin_deps.bzl
index 0db5af8..2d40d7d 100644
--- a/external_plugin_deps.bzl
+++ b/external_plugin_deps.bzl
@@ -1,8 +1,8 @@
 load("//tools/bzl:maven_jar.bzl", "maven_jar")
 
 def external_plugin_deps():
-  maven_jar(
-    name = 'metrics_jmx',
-    artifact = 'io.dropwizard.metrics:metrics-jmx:4.0.2',
-    sha1 = 'c8c14f6d66100a6b79f5d4b6de1d50ccc7f627fb',
-  )
+    maven_jar(
+        name = "metrics_jmx",
+        artifact = "io.dropwizard.metrics:metrics-jmx:4.0.2",
+        sha1 = "c8c14f6d66100a6b79f5d4b6de1d50ccc7f627fb",
+    )