Fix Edge ignoring pointer-events:none on button's span

[dpitois]

Fix for #12698

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

• Make sure that you propose PR to right branch: bugfix for master, feature for branch feature.
• 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.
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• 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.

No test added, I don't know how to test that change.
Change was tested on my computer with the following browsers:

• Chrome 70.0.3538.67
• Firefox 62.0.3 ESR
• IE 11.0.9600.19155

Would be nice, if some people could test/validate that change with Windows 10 and Edge to be sure there is no regression - I don't have the opportunity to access that kind of setup.

[codecov]

Codecov Report

Merging #12712 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #12712   +/-   ##
=======================================
  Coverage   92.34%   92.34%           
=======================================
  Files         211      211           
  Lines        5550     5550           
  Branches     1600     1561   -39     
=======================================
  Hits         5125     5125           
  Misses        421      421           
  Partials        4        4

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