REF: remove JoinUnit.shape
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit) for how to run them
- [ ] whatsnew entry

Can you please wait with further PRs to JoinUnit until the discussion in https://github.com/pandas-dev/pandas/pull/43507 is resolved? (since those might make it harder to revert the change) > Can you please wait with further PRs to JoinUnit until the discussion in #43507 is resolved? (since those might make it harder to revert the change)

@jorisvandenbossche if you don't like the new behavior then pls open an issue @jorisvandenbossche discussion is not happening. please open an issue if you disagree with current behavior. Can you respond to my comment at https://github.com/pandas-dev/pandas/pull/43507#issuecomment-920375856? This pull request is stale because it has been open for thirty days with no activity. Please update or respond to this comment if you're still interested in working on this. moving off 1.4 @jbrockmendel pls rebase, let's just do this