Change `ObjectArrayDeserializer` to use "generic" type parameter (`java.lang.Object`) to remove co-variant return type

[cowtowncoder]

Describe your Issue

Looking at stack traces, it looks like co-variant method calls induced by generic typing for JsonDeserializer adds one stack frame per call. While not performance issue in general, this can be problematic for deep call stacks which are possible for this specific type; and in particular for Fuzzer-generated scenarios. To reduce call stack depth, let's change parameterization to be plain old java.lang.Object (instead of current Object[]).