Format external_plugin_deps.bzl with buildifier

Change-Id: Ib31078c3db34c0799b4c6280dea60cc9940e0333
diff --git a/external_plugin_deps.bzl b/external_plugin_deps.bzl
index aac37f1..9325ea1 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_graphite',
-    artifact = 'io.dropwizard.metrics:metrics-graphite:4.0.2',
-    sha1 = 'c58939a16560d60d3f3d7fe941d2dc9f41ba3b6c',
-  )
+    maven_jar(
+        name = "metrics_graphite",
+        artifact = "io.dropwizard.metrics:metrics-graphite:4.0.2",
+        sha1 = "c58939a16560d60d3f3d7fe941d2dc9f41ba3b6c",
+    )