fix typos in builtin.rs doc #7107

Job	Run time
Linux x86-64	43m 47s
Linux Arm	19m 27s
Container Image	12m 1s
Docs	1m 38s
Mac Arm	10m 42s
Mac Intel	26m 3s
Repolinter	1m 13s
Stdlib	2m 4s
Windows	30m 0s
Mac Universal Binary	31s
Polkadot Integration test with subxt	4m 39s
Solana Integration test	3m 28s
Anchor Integration test	5m 56s
Polkadot Integration test	2m 29s
Soroban Integration test	11m 13s
Visual Code Extension	1m 49s
Coverage report	0s
	2h 57m 0s

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