treewide: fix invocations of installBin command

I've removed the trivial command in 4e72b61d.
I think `install -Dt "$out/bin"` is a better replacement anyway,
as it can be easily used to other directories than $out/bin.

/cc @ehmry who seems to maintain many packages with this usage.
(BTW, it would be better to have maintainer attribute same as github
username, as it makes pinging maintainers much easier.)