holidays: Update holidays using newest holidata.net data

Remove outdated holiday files that could not be updated.

doc/rc/holidays.en-GB.rc

@@ -1,9 +1,9 @@
 ###############################################################################
 # International Holiday Data provided by Holidata.net
-# http://holidata.net/en-GB/2015.json
-# http://holidata.net/en-GB/2016.json
+# https://holidata.net/en-GB/2020.json
+# https://holidata.net/en-GB/2021.json
 #
-# Copyright 2006 - 2016, Paul Beckingham, Federico Hernandez.
+# Copyright 2006 - 2020, Paul Beckingham, Federico Hernandez.
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files (the "Software"), to deal
@@ -28,34 +28,40 @@
 ###############################################################################
 
 holiday.en-GB1.name=New Year's Day
-holiday.en-GB1.date=20150101
+holiday.en-GB1.date=20200101
 holiday.en-GB2.name=Good Friday
-holiday.en-GB2.date=20150403
+holiday.en-GB2.date=20200410
 holiday.en-GB3.name=Easter Monday
-holiday.en-GB3.date=20150406
+holiday.en-GB3.date=20200413
 holiday.en-GB4.name=Early May Bank Holiday
-holiday.en-GB4.date=20150504
+holiday.en-GB4.date=20200504
 holiday.en-GB5.name=Spring Bank Holiday
-holiday.en-GB5.date=20150525
+holiday.en-GB5.date=20200525
 holiday.en-GB6.name=August Bank Holiday
-holiday.en-GB6.date=20150831
+holiday.en-GB6.date=20200831
 holiday.en-GB7.name=Christmas Day
-holiday.en-GB7.date=20151225
+holiday.en-GB7.date=20201225
 holiday.en-GB8.name=Boxing Day
-holiday.en-GB8.date=20151226
-holiday.en-GB9.name=New Year's Day
-holiday.en-GB9.date=20160101
-holiday.en-GB10.name=Good Friday
-holiday.en-GB10.date=20160325
-holiday.en-GB11.name=Easter Monday
-holiday.en-GB11.date=20160328
-holiday.en-GB12.name=Early May Bank Holiday
-holiday.en-GB12.date=20160502
-holiday.en-GB13.name=Spring Bank Holiday
-holiday.en-GB13.date=20160530
-holiday.en-GB14.name=August Bank Holiday
-holiday.en-GB14.date=20160829
-holiday.en-GB15.name=Christmas Day
-holiday.en-GB15.date=20161225
-holiday.en-GB16.name=Boxing Day
-holiday.en-GB16.date=20161226
+holiday.en-GB8.date=20201226
+holiday.en-GB9.name=Boxing Day (observed)
+holiday.en-GB9.date=20201228
+holiday.en-GB10.name=New Year's Day
+holiday.en-GB10.date=20210101
+holiday.en-GB11.name=Good Friday
+holiday.en-GB11.date=20210402
+holiday.en-GB12.name=Easter Monday
+holiday.en-GB12.date=20210405
+holiday.en-GB13.name=Early May Bank Holiday
+holiday.en-GB13.date=20210503
+holiday.en-GB14.name=Spring Bank Holiday
+holiday.en-GB14.date=20210531
+holiday.en-GB15.name=August Bank Holiday
+holiday.en-GB15.date=20210830
+holiday.en-GB16.name=Christmas Day
+holiday.en-GB16.date=20211225
+holiday.en-GB17.name=Boxing Day
+holiday.en-GB17.date=20211226
+holiday.en-GB18.name=Christmas Day (observed)
+holiday.en-GB18.date=20211227
+holiday.en-GB19.name=Boxing Day (observed)
+holiday.en-GB19.date=20211228