chore: improve ArgumentsMutatorFuzzTest

Remove `null` check because parameter is annotated with `NotNull`

Author: Marcono1234

selffuzz/src/test/java/com/code_intelligence/selffuzz/mutation/ArgumentsMutatorFuzzTest.java

@@ -112,13 +112,11 @@ void fuzzListOfMaps(@WithSize(max = 4) Map<String, Integer> nullableMap) {
 
   @SelfFuzzTest
   void fuzzListOfSets(@WithSize(max = 10) @NotNull Set<@NotNull Integer> setWithSize) {
-    if (setWithSize != null) {
-      assertThat(setWithSize.size()).isAtMost(10);
-    }
+    assertThat(setWithSize.size()).isAtMost(10);
   }
 
   @SelfFuzzTest
-  void fuzzListOfLists(List<@NotNull List<String>> nullableMap, List<List<Integer>> nullableList) {}
+  void fuzzListOfLists(List<@NotNull List<String>> list, List<List<Integer>> nullableList) {}
 
   @SelfFuzzTest
   void fuzzPrimitiveArrays(