refactor: popover fixes #285

[BANG88]

First of all, thank you for your contribution! :-)

Please makes sure that these checkboxes are checked before submitting your PR, thank you!

• Make sure that you follow antd's code convention.
• Run npm run lint and fix those errors before submitting in order to keep consistent code style.
• Rebase before creating a PR to keep commit history clear.
• Add some descriptions and refer relative issues for you PR.

Extra checklist:

if isBugFix :

• Make sure that you add at least one unit test for the bug which you had fixed.

elif isNewFeature :

• Update API docs for the component.
• Update/Add demo to demonstrate new feature.
• Update TypeScript definition for the component.
• Add unit tests for the feature.

[codecov]

Codecov Report

Merging #298 into master will decrease coverage by 0.06%.
The diff coverage is 71.79%.

@@            Coverage Diff             @@
##           master     #298      +/-   ##
==========================================
- Coverage   59.23%   59.17%   -0.07%     
==========================================
  Files         197      197              
  Lines        4958     4977      +19     
  Branches     1087     1090       +3     
==========================================
+ Hits         2937     2945       +8     
- Misses       2004     2015      +11     
  Partials       17       17

Flag	Coverage Δ
#rn	59.17% <71.79%> (-0.07%)	⬇️

Impacted Files	Coverage Δ
components/popover/demo/basic.tsx	86.95% <71.42%> (-7.79%)	⬇️
components/popover/index.tsx	72.97% <71.87%> (-22.49%)	⬇️

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