Fix clippy lints re: docs indentation + unused feature #842

Job	Run time
clippy	8m 29s
Cross build from macOS to Linux (FIPS) (x86_64-unknown-linux-gnu)	5m 4s
Cross build from macOS to Linux (x86_64-unknown-linux-gnu)	1m 44s
rustfmt	18s
Test features	6m 56s
Test FIPS integration	3m 16s
Test (stable)	2m 12s
Test (arm-android)	2m 10s
Test (arm64-android)	2m 5s
Test (i686-android)	3m 42s
Test (x86_64-android)	1m 59s
Test (aarch64-ios)	2m 30s
Test (aarch64-ios-sim)	2m 47s
Test (x86_64-ios)	2m 26s
Test (i686-linux)	2m 38s
Test (arm-linux)	2m 11s
Test (aarch64-linux)	2m 30s
Test (arm64-macos)	2m 12s
Test (x86_64-macos)	2m 40s
Test (x86_64-mingw)	5m 35s
Test (i686-msvc)	5m 10s
Test (x86_64-msvc)	5m 48s
	1h 14m 22s

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