tweak test

nullaway/src/test/java/com/uber/nullaway/jspecify/GenericDiamondTests.java

@@ -21,14 +21,22 @@ static class Foo<T extends @Nullable Object> {
                 static Foo<@Nullable Void> make() {
                   throw new RuntimeException();
                 }
+                static Foo<@Nullable String> makeNullableStr() {
+                  throw new RuntimeException();
+                }
               }
               static class Bar<T extends @Nullable Object> {
                 Bar(Foo<T> foo) {
                 }
               }
-              void test() {
+              void testNegative() {
+                // should be legal
                 Bar<@Nullable Void> b = new Bar<>(Foo.make());
               }
+              void testPositive() {
+                // BUG: Diagnostic contains:
+                Bar<String> b = new Bar<>(Foo.makeNullableStr());
+              }
             }
             """)
         .doTest();