ftp/curl: Update to 8.1.1

Upgrade to 8.1.0 broke the build on recent CURRENT and this version
contains a fix for that

PR: 271526
Reported by: O. Hartmann <ohartmann@walstatt.org>
Fixes: 5fae3323ed2f9a1d203ccaed617ed49dec9d85ce
Pointy hat to: garga
MFH: 2023Q2
Sponsored by: Rubicon Communications, LLC ("Netgate")

(cherry picked from commit ad3e4398e404b82a8a371808331e3f9c92638c37)