Remove -zapwallettxes

-zapwallettxes is made a hidden option to inform users that it is
removed and they should be using abandontransaction to do the stuck
transaction thing.

src/dummywallet.cpp

@@ -49,7 +49,6 @@ void DummyWalletInit::AddWalletOptions(ArgsManager& argsman) const
         "-walletdir=<dir>",
         "-walletnotify=<cmd>",
         "-walletrbf",
-        "-zapwallettxes=<mode>",
         "-dblogsize=<n>",
         "-flushwallet",
         "-privdb",