fix(next/antd): fix single value invalid in PreviewText.Cascader

[ifblooms]

Before submitting a pull request, please make sure the following is done...

• Ensure the pull request title and commit message follow the Commit Specific in English.
• Fork the repo and create your branch from master or formily_next.
• If you've added code that should be tested, add tests!
• If you've changed APIs, update the documentation.
• Ensure the test suite passes (npm test).
• Make sure your code lints (npm run lint) - we've done our best to make sure these rules match our internal linting guidelines.

Please do not delete the above content

---

What have you changed?

Close #2935

[codecov]

Codecov Report

Merging #2940 (c55eba9) into formily_next (a0ee0bd) will not change coverage.
The diff coverage is n/a.

@@              Coverage Diff              @@
##           formily_next    #2940   +/-   ##
=============================================
  Coverage         96.00%   96.00%           
=============================================
  Files               148      148           
  Lines              6379     6379           
  Branches           1713     1713           
=============================================
  Hits               6124     6124           
  Misses              255      255           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update bef5c71...c55eba9. Read the comment docs.