Remove explicit dependency on jgit-servlet

It's exported in plugin-api and this library is added to the deps
in gerrit_plugin() itself.

Change-Id: I1e49fa702cd5a57a9ce6fdcf132560ac75654060
diff --git a/BUCK b/BUCK
index e073074..2e4ffe4 100644
--- a/BUCK
+++ b/BUCK
@@ -26,10 +26,6 @@
     ':nullable-jsr305',
     ':soy',
   ],
-  # Deps shared with Gerrit but not in the plugin API.
-  provided_deps = [
-    '//lib/jgit:jgit-servlet',
-  ],
   resources = glob(['src/main/resources/**/*']),
   manifest_entries = [
     'Gerrit-PluginName: gitiles',