sc-tracing: swap atty with is-terminal (#2718)
`atty` is unmaintaned. See the advisory https://github.com/advisories/GHSA-g98v-hv3f-hcfr I picked is-terminal because rustix is already in-tree, so doesn't increase the dependency footprint, and I am not sure if we can rely on `IsTerminal` from the std because I am not sure what our MSRV.