Bundle commons-io since gerrit core no longer provides it

By removing Solr from gerrit core in

  7fe1752bfdae0c280170ce2759146dc55bb6cd36

commons-io is no longer provided by the environment.
Building this plugin still worked, but loading it failed with:

  com.google.gerrit.server.plugins.PluginInstallException: org/apache/commons/io/FilenameUtils
  [...]
  Caused by: java.lang.NoClassDefFoundError: org/apache/commons/io/FilenameUtils
  [...]
  fatal: Plugin failed to install. Cause: org/apache/commons/io/FilenameUtils

By moving commons-io to the explicit dependencies, the plugin loads
again with current gerrit core.

Change-Id: Ifb43baafc2d1ee190875802f3bc2a36fed5e7cef
diff --git a/BUCK b/BUCK
index 1b9dbf0..2e48ed9 100644
--- a/BUCK
+++ b/BUCK
@@ -14,12 +14,12 @@
   ],
   deps = [
     ':amqp-client',
+    '//lib/commons:io',
     ':guice-multibindings',
   ],
   provided_deps = [
     '//lib:gson',
     '//lib/commons:codec',
-    '//lib/commons:io',
     '//lib/commons:lang',
   ],
 )