Remove `MemoBytes` from `ShelleyTx` #18241

Job	Run time
Check branch history	11s
cabal-format	8s
build (9.6.7, ubuntu-latest)	11m 11s
build (9.8.4, ubuntu-latest)	9m 49s
build (9.10.2, ubuntu-latest)	7m 52s
fourmolu	45s
gen-hie	7m 34s
build (9.12.2, ubuntu-latest)	8m 21s
Check if formal-ledger-specifications SRP is valid	8s
codegen	0s
${{ matrix.package }}-${{ matrix.ghc }}-${{ matrix.os }}	0s
Tests completed	1s
Send a slack notification on \#ledger-internal if the nightly build failed	0s
	46m 0s

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