BUG: Fix qSlicerSslTest accounting for updated redirect to https://slicer.org

(1) The HTTP code has been changed from "302 Found" to "301 Moved Permanently"

See https://en.wikipedia.org/wiki/HTTP_302 and https://en.wikipedia.org/wiki/HTTP_301

(2) Accessing https://slicer.org does not return SSL error anymore.
Thanks to "eQuality Technology <info@equality-tech.com>", the SSL
certificates are kept up-to-date with "certbot-auto" and the grade
returned by SSL Labs is A (for the sites:
https://www.ssllabs.com/ssltest/analyze.html?d=slicer.org
https://www.ssllabs.com/ssltest/analyze.html?d=www.slicer.org
https://www.ssllabs.com/ssltest/analyze.html?d=wiki.slicer.org

Thanks: eQuality Technology <info@equality-tech.com>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@25529 3bd1e089-480b-0410-8dfb-8563597acbee