Remove some more raw string formatting forgotten in f4fb771.

Running pkg.upgrade without arguments worked, it was generating
`pkg upgrade --y` which is all right because the only possibility is
`--yes`.  But when running, for example, with dryrun=True, it ended up
generating `pkg upgrade --n` and `--n` and there are more than one
option that starts with `n`, `--no-install-scripts`, `--dry-run` and
`--no-repo-update`.

salt/modules/pkgng.py

@@ -1151,8 +1151,6 @@ def upgrade(*names, **kwargs):
         opts += 'n'
     if not dryrun:
         opts += 'y'
-    if opts:
-        opts = '-' + opts
 
     cmd = _pkg(jail, chroot, root)
     cmd.append('upgrade')