fix(watch): fix output text when no tasks are provided (#9612)
Additional fixes for https://github.com/vercel/turborepo/pull/9598
### Description
- Unified output texts from `some potential ones to run` to `some
potential ones` across both run and watch commands when no tasks are
provided. Let me know if there is a better way!
- Added documentation and tests.
### Testing Instructions
Added integration tests.
Co-authored-by: Anthony Shew <anthony.shew@vercel.com>