Fix downloading of URLs that end in a slash

* lisp/net/eww.el (eww-download-callback): Fix download URL
file name.  Previously this wasn't handling download URLs
correctly, resulting in all downloaded pages being named
"!", "!(1)", etc.  (Bug#34291)
1 job for emacs-26 in 42 minutes and 48 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Test
passed #759
test

00:42:48