update Hackage Matrix link

[ulysses4ever]

[andreasabel]

But I ain't working yet, the matrix.hackage.org. At least it does not display anything sensible...

Note how it blends the package I visited first (Agda) with the once I am viewing currently (MissingH):

[ulysses4ever]

Hm, this is sad. I tried it on one package (async), and simply changing the URL did seem to show something reasonable (I may be wrong of course).

I think if it shows something reasonable sometimes, it's already improvement upon the current state. But I understand (a) it may not, (b) you may disagree. In either case, please, feel free to close this PR.

[andreasabel]

Well, in the long run, we are likely going this way. But maybe we should hold back a little until matrix.hackage is working reasonably.

[gbaz]

cc: @davean