ftp/curl: Temporarily remove GSSAPI_BASE

Heimdal Kerberos support has been removed in cURL 8.17.0.
The Kerberos in base system will be replaced with MIT.
This option will be re-added when possible.

Reference: https://www.freebsd.org/status/report-2025-04-2025-06/mit_krb5/

		https://lists.freebsd.org/archives/freebsd-current/2025-June/007867.html