Less authoritative stable_sort_primitive message
fixes#8241
Hey all - first contribution here so I'm deciding to start with something small.
Updated the linked message to be less authoritative as well as moved the lint grouping from `perf` to `pedantic` as suggested by `@camsteffen` under the issue.
changelog: [`stable_sort_primitive`]: emit less authoritative message and move to `pedantic`
4c25880f0c