docs(module:input-number): typo correction

[CygnusRoboticus]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/NG-ZORRO/ng-zorro-antd/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[x] Documentation content changes
[ ] Application (the showcase website) / infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

Typo

Issue Number: N/A

What is the new behavior?

No more typo

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

N/A

[netlify]

Deploy preview for ng-zorro-master ready!

Built with commit 797ec5d

https://deploy-preview-3507--ng-zorro-master.netlify.com

[codecov]

Codecov Report

Merging #3507 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master   #3507      +/-   ##
=========================================
- Coverage    95.6%   95.6%   -0.01%     
=========================================
  Files         609     609              
  Lines       13250   13250              
  Branches     1810    1810              
=========================================
- Hits        12668   12667       -1     
  Misses        197     197              
- Partials      385     386       +1

Impacted Files	Coverage Δ
components/time-picker/time-holder.ts	96.57% <0%> (-0.69%)	⬇️

---

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 6342657...797ec5d. Read the comment docs.