Remove support for unicode_hex in chargeback currencies

Never been used and it would be need more work to add
more currencies.

app/models/chargeback_rate_detail_currency.rb

@@ -5,7 +5,6 @@ class ChargebackRateDetailCurrency < ApplicationRecord
   validates :name,        :presence => true, :length => {:maximum => 100}
   validates :full_name,   :presence => true, :length => {:maximum => 100}
   validates :symbol,      :presence => true, :length => {:maximum => 100}
-  validates :unicode_hex, :presence => true, :length => {:minimum => 1}
 
   has_many :chargeback_rate_detail, :foreign_key => "chargeback_rate_detail_currency_id"
 

db/fixtures/chargeback_rate_detail_currencies.yml

@@ -3,19 +3,15 @@
   :name: "Dollars"
   :full_name: "United States Dollars"
   :symbol: "$"
-  :unicode_hex: "36"
 - :code: "EUR"
   :name: "Euro"
   :full_name: "Euro"
   :symbol: "€"
-  :unicode_hex: "8364"
 - :code: "GBP"
   :name: "Pounds"
   :full_name: "Pound Sterling"
   :symbol: "£"
-  :unicode_hex: "163"
 - :code: "JPY"
   :name: "Yen"
   :full_name: "Japanese Yen"
-  :symbol: "¥"
-  :unicode_hex: "165"
+  :symbol: "¥"

spec/models/chargeback_rate_detail_currency_spec.rb

@@ -14,7 +14,4 @@
   it "is invalid without a symbol" do
     expect(FactoryGirl.build(:chargeback_rate_detail_currency, :symbol => nil)).not_to be_valid
   end
-  it "is invalid without a unicode_hex" do
-    expect(FactoryGirl.build(:chargeback_rate_detail_currency, :unicode_hex => nil)).not_to be_valid
-  end
 end