KT-20357: Add sample for Collections distinct and distinctBy methods

libraries/stdlib/samples/test/samples/collections/collections.kt

@@ -448,6 +448,13 @@ class Collections {
             assertPrints(withLengthOfNames, "{Grace Hopper=11, Jacob Bernoulli=14}")
         }
 
+        @Sample
+        fun distinctAndDistinctBy() {
+            val list = listOf('a', 'A', 'b', 'B', 'A', 'a')
+            assertPrints(list.distinct(), "[a, A, b, B]")
+            assertPrints(list.distinctBy { it.toUpperCase() }, "[a, b]")
+        }
+
         @Sample
         fun groupBy() {
             val words = listOf("a", "abc", "ab", "def", "abcd")