fix(module: tabbar): typescript error

[Eve-Sama]

close #750

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-mobile/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?

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

What is the current behavior?

Issue Number: 750

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[Eve-Sama]

TabBarItemComponent 继承自 TabPaneComponent
在 TabPaneComponent 中已经有了title的input与get set.
那么 TabBarItemComponent 本身也就有了, 没必要重新声明一次.
本地跑过单测了, 全部成功, 项目也run了, title没出现异常.

[codecov]

Codecov Report

Merging #753 into master will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #753      +/-   ##
==========================================
- Coverage   86.93%   86.93%   -0.01%     
==========================================
  Files         164      164              
  Lines        6635     6634       -1     
  Branches     1111     1111              
==========================================
- Hits         5768     5767       -1     
  Misses        422      422              
  Partials      445      445              

Impacted Files	Coverage Δ
components/tab-bar/tab-bar-item.component.ts	100.00% <ø> (ø)

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