Remove deprecated `pallet_balances`'s `set_balance_deprecated` and `transfer` dispatchables (#1226)

* remove deprecated dispatchables

* update test

* update tests

* update tests

* add prdocs

* add prdoc

* Update docs/prdoc/pr_1226.prdoc

Co-authored-by: Chevdor <chevdor@users.noreply.github.com>

* move prdoc file

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Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>
Co-authored-by: Chevdor <chevdor@users.noreply.github.com>