Deprecated reference to IEEE 754-2008 in W3C version

[chykon]

In the "References" section, the W3C version of the specification contains a reference to IEEE 754-2008 instead of IEEE 754-2019. Browser and PDF versions do not have this problem.

[ericprud]

might be about time for us to cut another draft anyways. that should grab the current refrences.

[sunfishcode]

At this time, the latest draft refers to IEEE 754-2019, but the URL still points to IEEE 754-2008. I've now submittted speced/bikeshed#2981 to update bikeshed to use IEEE 754-2019.

I've also now submitted #1852 to update the last few mentions of IEEE 754-2008 from the spec repo.