Equivalize isLowerCase and isUpperCase behavior in all platforms #KT-46184

libraries/stdlib/src/kotlin/text/Char.kt

@@ -296,9 +296,10 @@ public expect fun Char.isLetterOrDigit(): Boolean
 public expect fun Char.isDigit(): Boolean
 
 /**
- * Returns `true` if this character is an upper case letter.
+ * Returns `true` if this character is upper case.
  *
- * A character is considered to be an upper case letter if its [category] is [CharCategory.UPPERCASE_LETTER].
+ * A character is considered to be an upper case character if its [category] is [CharCategory.UPPERCASE_LETTER],
+ * or it has contributory property Other_Uppercase as defined by the Unicode Standard.
  *
  * @sample samples.text.Chars.isUpperCase
  */
@@ -306,9 +307,10 @@ public expect fun Char.isDigit(): Boolean
 public expect fun Char.isUpperCase(): Boolean
 
 /**
- * Returns `true` if this character is a lower case letter.
+ * Returns `true` if this character is lower case.
  *
- * A character is considered to be a lower case letter if its [category] is [CharCategory.LOWERCASE_LETTER].
+ * A character is considered to be a lower case character if its [category] is [CharCategory.LOWERCASE_LETTER],
+ * or it has contributory property Other_Lowercase as defined by the Unicode Standard.
  *
  * @sample samples.text.Chars.isLowerCase
  */