JapanProvider - remove Obsolete code

src/Nager.Date/PublicHolidays/JapanProvider.cs

@@ -62,19 +62,6 @@ public IEnumerable<PublicHoliday> GetHolidays(int year)
             return items.OrderBy(o => o.Date);
         }
 
-        /// <summary>
-        /// Get the Golden Week for a given year
-        /// </summary>
-        /// <see href="https://en.wikipedia.org/wiki/Golden_Week_(Japan)" />
-        /// <param name="year"></param>
-        [Obsolete("Not a holiday logic")]
-        public DateTime GetGoldenWeekStartDate(int year)
-        {
-            var showaDay = new DateTime(year, 4, 29).Shift(saturday => saturday, sunday => sunday.AddDays(1));
-
-            return showaDay;
-        }
-
         /// <summary>
         /// Adds the emperor's birthday based on the era/emperor of the current year.
         /// </summary>