Fix typos in tests/polkadot.rs (#1791) #7163

Job	Run time
Docs	1m 23s
Container Image	12m 13s
Linux Arm	19m 36s
Linux x86-64	35m 35s
Mac Arm	10m 41s
Mac Intel	20m 39s
Windows	9m 34s
Stdlib	2m 5s
Mac Universal Binary	0s
Anchor Integration test	0s
Polkadot Integration test	0s
Polkadot Integration test with subxt	0s
Solana Integration test	0s
Soroban Integration test	0s
Visual Code Extension	0s
Coverage report	0s
	1h 51m 46s

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