mail/libspf2: Update to 1.2.11

• Update MASTER_SITES

Changes: https://github.com/shevek/libspf2/commits/master
Security: CVE-2021-20314
PR: 259938
Reported by: Dmitriy <supportme@ukr.net>

(cherry picked from commit 97deffc5b76fc61eeef40559aa82d7999c698288)