vim-patch.sh: remove --posix from patch invocation

This was supposed to avoid creating *.orig. It doesn't do that, and
worse, it also seems to prevent new files from being created.

scripts/vim-patch.sh

@@ -234,7 +234,7 @@ stage_patch() {
   output="$(commit_message | git commit --allow-empty --file 2>&1 -)" &&
     echo "✔ ${output}" ||
     (echo "✘ ${output}"; false)
-
+
   if test -n "$try_apply" ; then
     if ! check_executable patch; then
       printf "\n✘ 'patch' command not found\n"