Move EE hierarchy specs to a separate file

This moves the specs for ObjectHierarchy#root to a separate spec file,
ensuring the file shared between CE and EE is the same for both.

ee/spec/lib/gitlab/object_hierarchy_spec.rb

+require 'spec_helper'
+
+describe Gitlab::ObjectHierarchy do
+  let!(:parent) { create(:group) }
+  let!(:child1) { create(:group, parent: parent) }
+  let!(:child2) { create(:group, parent: child1) }
+
+  describe '#root' do
+    it 'includes only the roots' do
+      relation = described_class.new(Group.where(id: child2)).roots
+
+      expect(relation).to contain_exactly(parent)
+    end
+
+    it 'when quering parent it includes parent' do
+      relation = described_class.new(Group.where(id: parent)).roots
+
+      expect(relation).to contain_exactly(parent)
+    end
+  end
+end

spec/lib/gitlab/object_hierarchy_spec.rb

@@ -145,20 +145,6 @@ describe Gitlab::ObjectHierarchy do
     end
   end
 
-  describe '#root' do
-    it 'includes only the roots' do
-      relation = described_class.new(Group.where(id: child2)).roots
-
-      expect(relation).to contain_exactly(parent)
-    end
-
-    it 'when quering parent it includes parent' do
-      relation = described_class.new(Group.where(id: parent)).roots
-
-      expect(relation).to contain_exactly(parent)
-    end
-  end
-
   describe '#all_objects' do
     let(:relation) do
       described_class.new(Group.where(id: child1.id)).all_objects