Fix block v3 reward encodings #14902

Job	Run time
target-branch-check	1s
beacon-chain-tests	1s
network-tests	16m 38s
debug-tests-ubuntu	1s
ef-tests-ubuntu	1s
op-pool-tests	19m 27s
release-tests-ubuntu	1s
release-tests-windows	1s
slasher-tests	5m 22s
state-transition-vectors-ubuntu	11m 20s
cargo-udeps	6m 31s
check-code	7m 42s
check-msrv	4m 20s
cli-check	17m 58s
compile-with-beta-compiler	12m 40s
dockerfile-ubuntu	13m 33s
doppelganger-protection-test	1s
eth1-simulator-ubuntu	26m 53s
execution-engine-integration-ubuntu	1s
merge-transition-ubuntu	27m 17s
no-eth1-simulator-ubuntu	27m 24s
syncing-simulator-ubuntu	22m 27s
test-suite-success	1s
	3h 39m 41s

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