Re-enable SHA1 for signing to match Firefox's TLS fingerprint

While even tor tries to mimic Firefox PBM (https://gitlab.torproject.org/tpo/core/tor/-/blob/main/src/lib/tls/ciphers.inc), you decided to deviate from its fingerprint in https://gitlab.torproject.org/tpo/applications/tor-browser/-/blob/e2b56df193f8a03bd66d074f0860e814317161cf/browser/app/profile/001-base-profile.js#L158-161