fix(submit:phabricator): don't update diffs with --verbatim

The `--verbatim` flag updates the phab's "reviewers" field, among others. If Herald added reviewers, or if somebody not in your reviewers list accepted the diff, then running `git submit` would revert the "reviewers" field and you would lose your accepts, which is a bad experience. There is a successful workflow where you run `arc amend` before ever running `arc diff` to update the diff, but it's probably better to do the least surprising thing, which is to preserve the state on Phabricator (since mutating it may have side effects, unlike the local commit message).

git-branchless-submit/src/phabricator.rs

@@ -615,7 +615,7 @@ Differential Revision: https://phabricator.example.com/D000$(git rev-list --coun
                 .map_err(Error::BuildRebasePlan)?;
         let test_options = ResolvedTestOptions {
             command: if !should_mock() {
-                let mut args = vec!["arc", "diff", "--verbatim", "--head", "HEAD", "HEAD^"];
+                let mut args = vec!["arc", "diff", "--head", "HEAD", "HEAD^"];
                 args.extend(match message {
                     Some(message) => ["-m", message.as_ref()],
                     None => ["-m", "update"],