Fix `clippy::manual_ignore_case_cmp` lint #751

Job	Run time
cargo test (windows-latest)	1m 36s
cargo test (macos-latest)	37s
formatting	27s
cargo check (msrv) (android) (armv7-linux-androideabi)	27s
cargo check (msrv) (windows-latest)	1m 24s
cargo test (ubuntu-latest)	34s
cargo check (msrv) (android) (aarch64-linux-android)	41s
cargo check (msrv) (macos-latest)	30s
cargo check (msrv) (android) (x86_64-linux-android)	49s
cargo clippy (windows-latest)	2m 8s
cargo check (msrv) (ubuntu-latest)	24s
cargo clippy (android) (armv7-linux-androideabi)	53s
cargo clippy (macos-latest)	1m 2s
cargo clippy (android) (aarch64-linux-android)	1m 46s
cargo clippy (ubuntu-latest)	1m 1s
cargo doc (windows-latest)	2m 14s
typos	5s
cargo clippy (android) (x86_64-linux-android)	1m 40s
cargo doc (macos-latest)	1m 7s
cargo doc (ubuntu-latest)	1m 20s
	20m 45s

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