Update zip_codes.xml patterns for Guernsey

Update zip_codes.xml patterns for Guernsey to support GY10 postcodes for the Island of Sark e.g. https://en.wikipedia.org/wiki/GY_postcode_area

Author: DrJohnM

app/code/Magento/Directory/etc/zip_codes.xml

@@ -259,6 +259,7 @@
     <zip countryCode="GG">
         <codes>
             <code id="pattern_1" active="true" example="AB1 2CD">^[a-zA-Z]{2}[0-9]{1}\s[0-9]{1}[a-zA-Z]{2}$</code>
+            <code id="pattern_2" active="true" example="AB12 3CD">^[a-zA-Z]{2}[0-9]{2}\s?[0-9]{1}[a-zA-Z]{2}$</code>
         </codes>
     </zip>
     <zip countryCode="GH">