Bump niffler from 2.6.0 to 2.7.0 #6352

Job	Run time
Check	23s
Check if cbindgen runs cleanly for generating the C headers	1m 11s
coverage	2m 8s
Lints (beta)	26s
minimum_rust_version	32s
Publish (on tags, dry-run otherwise)	13m 14s
Lints (stable)	41s
test_all_features	2m 39s
test (beta)	51s
Check if wasm-pack builds a valid package for the sourmash crate	48s
test (stable)	44s
test (windows)	3m 11s
test (macos)	1m 32s
	28m 20s

Provide feedback