testing: change List to more common Iterable

Author: alxkm

src/test/java/com/thealgorithms/recursion/GenerateSubsetsTest.java

@@ -33,7 +33,7 @@ void testEmptyInput() {
         assertSubsets("", List.of(""));
     }
 
-    private void assertSubsets(String input, List<String> expected) {
+    private void assertSubsets(String input, Iterable<String> expected) {
         List<String> actual = GenerateSubsets.subsetRecursion(input);
         assertIterableEquals(expected, actual, "Subsets do not match for input: " + input);
     }