Fix for Clippy `HSTRING` interior mutability warnings in nightly #2304

Job	Run time
check (stable, x86_64-pc-windows-msvc, x86_64-pc-windows-msvc)	17m 58s
check (nightly, x86_64-pc-windows-msvc, i686-pc-windows-msvc)	20m 3s
check (nightly, x86_64-pc-windows-gnu, x86_64-pc-windows-gnu)	23m 34s
check (stable, x86_64-pc-windows-gnu, i686-pc-windows-gnu)	21m 25s
check (stable, x86_64-pc-windows-msvc, aarch64-pc-windows-msvc, --no-run)	16m 59s
check (nightly, x86_64-pc-windows-msvc, aarch64-pc-windows-msvc, --no-run)	17m 32s
	1h 57m 31s

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