cfitsio: use HTTP URL instead of FTP

The NASA HEASARC FTP server is currently not responding via FTP, but
allows HTTP indexes and downloads. SHA1 matches and doesn't need to
changed. The directy index is linked to from
http://heasarc.gsfc.nasa.gov/docs/software/fitsio/fitsio.html

Fixes #23049.
Closes #23085.

Signed-off-by: Misty De Meo <mistydemeo@gmail.com>