Removed `Milestone#is_empty?`

Removed `Milestone#is_empty?` because is not used anymore in the codebase

app/models/milestone.rb

@@ -153,10 +153,6 @@ class Milestone < ActiveRecord::Base
     active? && issues.opened.count.zero?
   end
 
-  def is_empty?(user = nil)
-    total_items_count(user).zero?
-  end
-
   def author_id
     nil
   end

changelogs/unreleased/30056-rename-milestones-empty.yml

+---
+title: Removed Milestone#is_empty?
+merge_request: 10523
+author: Jacopo Beschi @jacopo-beschi

spec/models/milestone_spec.rb

@@ -109,18 +109,6 @@ describe Milestone, models: true do
     it { expect(milestone.percent_complete(user)).to eq(75) }
   end
 
-  describe '#is_empty?' do
-    before do
-      milestone.issues << create(:issue, project: project)
-      milestone.issues << create(:closed_issue, project: project)
-      milestone.merge_requests << create(:merge_request)
-    end
-
-    it { expect(milestone.closed_items_count(user)).to eq(1) }
-    it { expect(milestone.total_items_count(user)).to eq(3) }
-    it { expect(milestone.is_empty?(user)).to be_falsey }
-  end
-
   describe '#can_be_closed?' do
     it { expect(milestone.can_be_closed?).to be_truthy }
   end