README: Fix broken link.
README: Fix broken link.

I'd apparently lost the footnote part of the footnote link, but @gsilvis and I
are in agreement that this was kindof gross anyway -- "click here" is not
something one should write in a document that may be read in source form.
I've reworded slightly instead.
SahilTikale/switchHaaS,apoorvemohan/haas,kylehogan/hil,kylehogan/haas,henn/hil_sahil,lokI8/haas,SahilTikale/haas,apoorvemohan/haas,henn/hil,henn/hil_sahil,henn/hil,meng-sun/hil,kylehogan/hil,meng-sun/hil,CCI-MOC/haas,henn/haas