Bump handlebars from 4.5.0 to 5.1.2 #1669

Job	Run time
check	2m 48s
clippy	3m 49s
rustfmt	10s
test	11m 51s
audit	16s
cross-armv7	43s
integration-test-five-nodes	12m 19s
cross-aarch64	45s
integration-test-multi-exit	12m 32s
integration-test-althea-payment	16m 22s
integration-test-db-migration	12m 20s
integration-test-debts	4h 12m 25s
integration-test-eth-payments	21m 45s
integration-test-validate-contract	12m 15s
	6h 0m 20s

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