security/nss: update to 3.81

Changes: https://groups.google.com/a/mozilla.org/g/dev-tech-crypto/c/jYrL4b47r3A
Changes: https://hg.mozilla.org/projects/nss/shortlog/NSS_3_81_RTM
Reported by: Repology

(cherry picked from commit 2c915c4b5437032198ac9ab646373c82327a5231)