masonry: Fix `unnecessary_mut_passed` lints. #311

Job	Run time
cargo fmt	9s
cargo doc (windows-latest)	3m 8s
cargo clippy + test (windows-latest)	6m 34s
cargo doc (macos-latest)	1m 34s
cargo clippy + test (macos-latest)	2m 22s
cargo doc (ubuntu-latest)	1m 29s
cargo clippy + test (ubuntu-latest)	3m 39s
	18m 55s

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