Follow-up to b340ecd — the doc comment on
`warmup_period_matches_first_some_for_every_parameter_set` had an
unbalanced inline-code span ("`Some``") that tripped
`clippy::doc_invalid_doc_attributes` (caught by `clippy -D warnings`
but not by `cargo build` or `cargo test`). Rephrased the sentence so
every backtick is paired. No code change, no test change.