Bump handlebars from 5.1.2 to 6.1.0 #2014

Job	Run time
check	3m 8s
rustfmt	3s
clippy	3m 48s
audit	16s
test	11m 28s
integration-test-althea-payment	17m 3s
integration-test-db-migration	11m 14s
integration-test-eth-payments	15m 15s
integration-test-debts	15m 13s
integration-test-five-nodes	11m 16s
integration-test-multi-exit	11m 16s
integration-test-validate-contract	11m 4s
cross-armv7	42s
cross-aarch64	39s
	1h 52m 25s

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