Fix New Years Day tests of South Korea.

The holiday 'twoDaysLaterNewYearsDay' has been removed from 1990,
however the unit test for the name and holiday type allowed the possible
testing range to include the year 1990.

Signed-off-by: Sacha Telgenhof <me@sachatelgenhof.com>

tests/SouthKorea/NewYearsDayTest.php

@@ -122,7 +122,7 @@ public function testTranslation(): void
         $this->assertTranslatedHolidayName(
             self::REGION,
             'twoDaysLaterNewYearsDay',
-            $this->generateRandomYear(self::ESTABLISHMENT_YEAR, 1990),
+            $this->generateRandomYear(self::ESTABLISHMENT_YEAR, 1989),
             [self::LOCALE => '새해 연휴']
         );
     }
@@ -149,7 +149,7 @@ public function testHolidayType(): void
         $this->assertHolidayType(
             self::REGION,
             'twoDaysLaterNewYearsDay',
-            $this->generateRandomYear(self::ESTABLISHMENT_YEAR, 1990),
+            $this->generateRandomYear(self::ESTABLISHMENT_YEAR, 1989),
             Holiday::TYPE_OFFICIAL
         );
     }