Complete Korean translation for boolean and null predicates (#1588)

* Initial plan

* Complete Korean translation for boolean and null predicates

Co-authored-by: scarroll32 <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: scarroll32 <[email protected]>

Author: Copilot

lib/ransack/locale/ko.yml

@@ -62,9 +62,9 @@ ko:
       not_end: "끝나지 않음"
       not_end_any: "어떤 것이든 끝나지 않음"
       not_end_all: "모두 끝나지 않음"
-      'true': "is true"
-      'false': "is false"
-      present: "is present"
-      blank: "is blank"
-      'null': "is null"
-      not_null: "is not null"
+      'true': "참"
+      'false': "거짓"
+      present: "존재함"
+      blank: "비어있음"
+      'null': "널"
+      not_null: "널이 아님"