ci: remove orphaned nss_install_smoke workflow (#1360)

NSS was removed from autofit (the [nss] extra and af.NSS are both gone from
main), but nss_install_smoke.yml was left behind. It runs on every PR and does
`pip install -e PyAutoFit[nss]` — an extra that no longer exists — so it fails
on every PR ("autofit 1.0.dev0 does not provide the extra 'nss'"). Delete it;
it validates a removed feature.

Co-authored-by: Jammy2211 <JNightingale2211@gmail.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: 3 people