MRG: update rust CHANGELOG in preparation for r0.18.0 (#3450) #6174

Job	Run time
Check	21s
coverage	8m 57s
test (beta)	1m 26s
test (stable)	1m 20s
test_all_features	12m 28s
test (windows)	4m 37s
Lints (beta)	33s
Check if wasm-pack builds a valid package for the sourmash crate	1m 20s
test (macos)	1m 15s
Lints (stable)	29s
minimum_rust_version	6m 27s
Run tests under wasm32-wasi	1m 11s
Publish (on tags, dry-run otherwise)	5m 20s
Check if cbindgen runs cleanly for generating the C headers	7m 54s
	53m 38s

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