StringArraySerializer claims type is immutable; shouldn't

Looking at default `TypeSerializer` instances I noticed what looks like a minor flaw, unless I am missing something.
Whereas all other array serializers indicate that type is not immutable (since in Java, arrays are not immutable), `StringArraySerializer` has:

```
@Override
public boolean isImmutableType()

```

and I think it should instead return `false`. I could create a PR, but seems like a small enough thing that issue report makes more sense.
I tried looking for deps to see if there's a test for this, but couldn't find one; otherwise could submit a test fix.