runtime(netrw): do not double escape Vim special characters

runtime(netrw): do not double escape Vim special characters

This double escaping was likely introduced because it was the only way
to make :Open work with hashes/percent signs despite shellescape(..., 1)
supposedly taking care of it, but then breaks the gx mapping
on MSYS2 as reported at [0]

Since special characters in the URL following :Open can be escaped,
whereas gx simply breaks and is more common, no longer double escape

[0]: https://github.com/vim/vim/issues/16252

fixes: #16252
closes: #16265

Signed-off-by: Konfekt <Konfekt@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>