[FEA] Unused variable in JNI/Java binding for `readParquet`

[ttnghia]

This is not a complete FEA but is closed to it. Currently, from Java we pass in a boolean variable binaryToString to JNI readParquet but it is unused after merging #11524. This variable may be used in the future thus we didn't remove it.

This issue is to track that unused variable.

[ttnghia]

CC @sameerz @revans2.

[GregoryKimball]

@revans2 should we remove the variable now?

[revans2]

We can remove it whenever. It is just a question of finding time to do the code cleanup.