Simplify basic presence validations (#29664)

spec/models/custom_emoji_category_spec.rb

@@ -4,11 +4,6 @@ require 'rails_helper'
 
 RSpec.describe CustomEmojiCategory do
   describe 'validations' do
-    it 'validates name presence' do
-      record = described_class.new(name: nil)
-
-      expect(record).to_not be_valid
-      expect(record).to model_have_error_on_field(:name)
-    end
+    it { is_expected.to validate_presence_of(:name) }
   end
 end