MRG: add comment about semver and column headings #6101

Job	Run time
test_all_features	13m 51s
test (beta)	1m 32s
test (stable)	1m 31s
test (windows)	3m 22s
test (macos)	1m 16s
Check	24s
Check if cbindgen runs cleanly for generating the C headers	8m 58s
coverage	10m 30s
Lints (beta)	34s
Publish (on tags, dry-run otherwise)	6m 25s
Lints (stable)	26s
Run tests under wasm32-wasi	1m 11s
Check if wasm-pack builds a valid package for the sourmash crate	1m 23s
minimum_rust_version	7m 40s
	59m 3s

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