Remove unnecessary library declaration

A dependency to the 'plugin-lib' is declared but not used.

Change-Id: I87a1cb42a1282345cd937f554e2f7042de9c499c
diff --git a/BUCK b/BUCK
index 4aaaec6..f6de1af 100644
--- a/BUCK
+++ b/BUCK
@@ -12,10 +12,3 @@
     'Gerrit-HttpModule: com.googlesource.gerrit.plugins.serverconfig.HttpModule',
   ]
 )
-
-maven_jar(
-  name = 'plugin-lib',
-  id = 'com.google.gerrit:gerrit-plugin-api:' + API_VERSION,
-  repository = REPO,
-  license = 'Apache2.0',
-)