Revert "Add VietName lunar calendar"

[gouguoyin]

Reverts golang-module/carbon#221

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (dd4b00c) 100.00% compared to head (cceac42) 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #222   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           22        22           
  Lines         2563      2553   -10     
=========================================
- Hits          2563      2553   -10     

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[culy247]

@gouguoyin why merge and revert feature/vi-lunar branch?
Are there any problem with this branch?

[gouguoyin]

@gouguoyin why merge and revert feature/vi-lunar branch? Are there any problem with this branch?

Do not recalculate Julian days in the Gregorian calendar, use calendar/Julian pakage
for example

julian.FromGregorian(time.Date(year, time.Month(month), day, 0, 0, 0, 0, time.Local)).ToJulian().JD(0)