Update Korean Translations for Before/After Context (#858)

* Translation update: fixed Korean before/after translations.

Translation update: fixed Korean before/after translations.

* Fix: Update test expectation for `diff_for_humans`

- Updated the expected output in 'test_diff_for_humans' to "1초 후" for consistency with the implementation.
- This resolves the mismatch between the test expectation and the actual output of 'diff_for_humans'.

* test: swap "뒤" and "앞" in test descriptions

src/pendulum/locales/ko/custom.py

@@ -6,8 +6,8 @@
 
 translations = {
     # Relative time
-    "after": "{0} 뒤",
-    "before": "{0} 앞",
+    "after": "{0} 후",
+    "before": "{0} 전",
     # Date formats
     "date_formats": {
         "LTS": "A h시 m분 s초",

tests/localization/test_ko.py

@@ -59,8 +59,8 @@ def diff_for_humans():
 
     d = pendulum.now().add(seconds=1)
     d2 = pendulum.now()
-    assert d.diff_for_humans(d2, locale=locale) == "1초 뒤"
-    assert d2.diff_for_humans(d, locale=locale) == "1초 앞"
+    assert d.diff_for_humans(d2, locale=locale) == "1초 후"
+    assert d2.diff_for_humans(d, locale=locale) == "1초 전"
 
     assert d.diff_for_humans(d2, True, locale=locale) == "1초"
     assert d2.diff_for_humans(d.add(seconds=1), True, locale=locale) == "2초"