Remove unused methods from StreamEntriesHelper (#1365)

Removes:

- avatar_for_status_url
- relative_time
- reblogged_by_me_class
- favourited_by_me_class

spec/helpers/stream_entries_helper_spec.rb

@@ -15,23 +15,7 @@ RSpec.describe StreamEntriesHelper, type: :helper do
     end
   end
 
-  describe '#avatar_for_status_url' do
-    pending
-  end
-
   describe '#entry_classes' do
     pending
   end
-
-  describe '#relative_time' do
-    pending
-  end
-
-  describe '#reblogged_by_me_class' do
-    pending
-  end
-
-  describe '#favourited_by_me_class' do
-    pending
-  end
 end