Replaces US Indigenous People's Day with International Indigenous People's Day (#55458)

Title. This modifies a unit test that tested the holiday I'm removing to test mother's day instead, as International Indigenous People's Day isn't an nth week holiday.

code/modules/holiday/holidays.dm

@@ -577,6 +577,14 @@
 /datum/holiday/hotdogday/greet()
 	return "Happy National Hot Dog Day!"
 
+/datum/holiday/indigenous //Indigenous Peoples' Day from Earth!
+	name = "International Day of the World's Indigenous Peoples"
+	begin_month = AUGUST
+	begin_day = 9
+
+/datum/holiday/indigenous/getStationPrefix()
+	return pick("Endangered language", "Word", "Language", "Language revitalization", "Potato", "Corn")
+
 /datum/holiday/hebrew
 	name = "If you see this the Hebrew holiday calendar code is broken"
 

code/modules/holiday/nth_week.dm

@@ -42,13 +42,6 @@
 	begin_month = OCTOBER
 	begin_weekday = MONDAY
 
-/datum/holiday/nth_week/indigenous
-	// not Columbus day anymore get rekt, Columbus
-	name = "Indigenous Peoples' Day"
-	begin_week = 2
-	begin_month = OCTOBER
-	begin_weekday = MONDAY
-
 /datum/holiday/nth_week/mother
 	name = "Mother's Day"
 	begin_week = 2

code/modules/unit_tests/holidays.dm

@@ -14,9 +14,9 @@
 	TEST_ASSERT(thanksgiving.shouldCelebrate(26, NOVEMBER, 2020, THURSDAY), "November 26, 2020 was not Thanksgiving.")
 
 // another nth day of week
-/datum/unit_test/indigenous_3683/Run()
-	var/datum/holiday/nth_week/indigenous/indigenous = new
-	TEST_ASSERT(indigenous.shouldCelebrate(11, OCTOBER, 3683, MONDAY), "October 11, 3683 was not Indigenous Peoples' Day.")
+/datum/unit_test/mother_3683/Run()
+	var/datum/holiday/nth_week/mother/mother = new
+	TEST_ASSERT(mother.shouldCelebrate(9, MAY, 3683, 2, SUNDAY), "May 9, 3683 was not Mother's Day.")
 
 // plain old simple holiday
 /datum/unit_test/hello_2020/Run()