remove not used method

app/models/charge.rb

@@ -61,12 +61,6 @@ def supports_grouped_by?
     standard? || dynamic?
   end
 
-  def basic_rate_percentage?
-    return false unless percentage?
-
-    properties.keys == ['rate']
-  end
-
   def equal_properties?(charge)
     charge_model == charge.charge_model && properties == charge.properties
   end

spec/models/charge_spec.rb

@@ -546,20 +546,6 @@
     end
   end
 
-  describe '#basic_rate_percentage?' do
-    it 'returns false if charge model is not percentage' do
-      expect(build(:standard_charge)).not_to be_basic_rate_percentage
-    end
-
-    it 'returns false if charge model is percentage but has other properties except rate' do
-      expect(build(:charge, charge_model: 'percentage', properties: {fixed_amount: '20'})).not_to be_basic_rate_percentage
-    end
-
-    it 'returns true only if properties of percentage charge contain only rate' do
-      expect(build(:charge, charge_model: 'percentage', properties: {rate: '0.20'})).to be_basic_rate_percentage
-    end
-  end
-
   describe '#equal_properties?' do
     let(:charge1) { build(:standard_charge, properties: {amount: 100}) }