make sure to update the UI when deleting a transaction (Jonas Schnelli)
Pull request description:
`CWallet::ZapSelectTx` removes transactions from the internal model, but leaves the UI in the dark.
Adding a `NotifyTransactionChanged()` should avoid having invalid transactions in the GUI.
Fixes #16950
https://github.com/bitcoin/bitcoin/pull/16952/commits/addaf8af8268d918973883a304025d40af5a33c1
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Backport of Core PR16952