Remove `MemoBytes` from `ShelleyTx` #18260

Job	Run time
cabal-format	8s
gen-hie	7m 3s
build (9.6.7, ubuntu-latest)	14m 24s
fourmolu	47s
shellcheck	8s
build (9.8.4, ubuntu-latest)	14m 24s
build (9.10.2, ubuntu-latest)	14m 25s
build (9.12.2, ubuntu-latest)	14m 24s
Check branch history	10s
Check if formal-ledger-specifications SRP is valid	6s
codegen	1s
${{ matrix.package }}-${{ matrix.ghc }}-${{ matrix.os }}	1s
Tests completed	1s
Send a slack notification on \#ledger-internal if the nightly build failed	1s
	1h 6m 3s

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