chore: fix doc typos for keys #1501

Job	Run time
Test 32-bit version	36s
Format - nightly toolchain	12s
Docs - stable toolchain (recent)	21s
Test - 1.63.0 toolchain (minimal)	5m 16s
Prepare	6s
Test - 1.63.0 toolchain (recent)	5m 17s
Test - stable toolchain (minimal)	3m 25s
WASM - stable toolchain	1m 48s
Test - stable toolchain (recent)	3m 39s
Docs - nightly toolchain (recent)	30s
Bench - nightly toolchain (recent)	26s
Test - nightly toolchain (minimal)	2m 30s
Lint - nightly toolchain (recent)	23s
no-std - nightly toolchain (recent)	41s
Test - nightly toolchain (recent)	2m 40s
ASAN - nightly toolchain (recent)	1m 35s
	29m 25s

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