Reword paragraph about jj and other VCS in README
Fixes two pedantic issues with this paragraph:
* "either" describing more than two things
* I am not an expert, but I suspect that Pijul
supports "automatic rebase".
@@ -24,7 +24,7 @@ features from Git (data model,
[speed](https://github.com/martinvonz/jj/discussions/49)), Mercurial (anonymous
branching, simple CLI [free from "the index"](docs/git-comparison.md#the-index),
[revsets](docs/revsets.md), powerful history-rewriting), and Pijul/Darcs
-([first-class conflicts](docs/conflicts.md)), with features not found in either
+([first-class conflicts](docs/conflicts.md)), with features not found in most
of them ([working-copy-as-a-commit](docs/working-copy.md),
[undo functionality](docs/operation-log.md), automatic rebase,
[safe replication via `rsync`, Dropbox, or distributed file
