runtime(netrw): prefer scp over pscp
regression introduced in ce2ad9ffd79fe6b2307cd46b9
The current logic is a bit funny, in that it checks for an executable of
scp, then pscp and if neither exists, it uses: scp :/
Anyway, let's fall back to the logic used before the above commit.
related: vim/vim#1473943f2edc096
Co-authored-by: Christian Brabandt <cb@256bit.org>