6.4 has passed its EOL date (2021-03), so it should not be listed in the
top release table any longer.

Fixes: #94

Thank you to Martin

rebuilt on commit.

also rename duplicate links

People tell me our home page was confusing, maybe this helps at least a
bit. But I guess the main reason will be the shift towards shorter
attention spans.

Remove the defunct 6.5.0 release from the convenient top list of releases
and pointers, to discourage its use. It's still listed on the total list
of releases of course.