Use #describe with String arg not symbol

See core commit:
http://github.com/opf/openproject/commit/3785fdc9edb187b9e5239879d6f5e41
1a10ae3df

spec/models/meeting_spec.rb

@@ -136,7 +136,7 @@ describe Meeting, type: :model do
     it { expect(meeting.watchers.collect(&:user)).to match_array([user1, user2]) }
   end
 
-  describe :close_agenda_and_copy_to_minutes do
+  describe '#close_agenda_and_copy_to_minutes' do
     before do
       agenda # creating it
 

spec/support/plugin_spec_helper.rb

@@ -20,7 +20,7 @@
 
 module PluginSpecHelper
   shared_examples_for 'customized journal class' do
-    describe :save do
+    describe '#save' do
       let(:text) { 'Lorem ipsum' }
       let(:changed_data) { { text: [nil, text] } }