Remove redundant dependency to commons-io

The commons-io library is a dependency of Gerrit core and Gerrit plugins
have access to Gerrit core dependencies.. Hence there is no need to add
it redundantly as a plugin dependency which had the effect that we
shade a different version of this library into the plugin jar.

Change-Id: Ifc7d5486ca9a07cc365639aec23367ae8ac7f3fe

external_plugin_deps.bzl

diff --git a/external_plugin_deps.bzl b/external_plugin_deps.bzl
index 40743be..4141942 100644
--- a/external_plugin_deps.bzl
+++ b/external_plugin_deps.bzl
@@ -2,11 +2,6 @@
 
 def external_plugin_deps():
     maven_jar(
-        name = "commons-io",
-        artifact = "commons-io:commons-io:2.2",
-        sha1 = "83b5b8a7ba1c08f9e8c8ff2373724e33d3c1e22a",
-    )
-    maven_jar(
         name = "mime-types",
         artifact = "org.overviewproject:mime-types:2.0.0",
         sha1 = "af05afd015df62cc6b949792e59dff97e403fcea",