remove deprecated field: privateTransaction.hash

[macfarla]

This field has been deprecated for some time:
// Caches the hash used to uniquely identify the transaction.
// This field will be removed in 1.5.0
@deprecated(since = "1.4.3")
protected volatile Hash hash;

• confirm it can safely be removed
• changelog entry

[mohitsaxenaknoldus]

Please assign it to me, I'll do it.

[macfarla]

thanks @mohitsaxenaknoldus it's yours!

[macfarla]

I can't seem to assign it to you. I'll also assign it to myself so nobody else picks it up.

[mohitsaxenaknoldus]

@macfarla PR: #3110

[macfarla]

This one is complete!