fix(module:tooltip): fix hiding when hover popover

[wzhudev]

close #4417

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?

[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: N/A

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[ ] No

Other information

[codecov]

Codecov Report

Merging #4418 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #4418      +/-   ##
==========================================
+ Coverage   92.23%   92.24%   +<.01%     
==========================================
  Files         522      522              
  Lines       11104    11104              
  Branches     2016     2017       +1     
==========================================
+ Hits        10242    10243       +1     
  Misses        435      435              
+ Partials      427      426       -1

Impacted Files	Coverage Δ
...mponents/tooltip/base/nz-tooltip-base.directive.ts	93.75% <100%> (ø)	⬆️
components/time-picker/time-holder.ts	96.49% <0%> (+0.87%)	⬆️

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