fix: Spin size not correct when set fontSize

[zombieJ]

🤔 This is a ...

• New feature
• Bug fix
• Site / document update
• Component style update
• TypeScript definition update
• Refactoring
• Code style optimization
• Test Case
• Branch merge
• Other (about what?)

👻 What's the background?

close #15206

💡 Solution

Use em unit.

📝 Changelog

Fix Spin size not correct when set fontSize

☑️ Self Check before Merge

• Doc is updated/provided or not needed
• Demo is updated/provided or not needed
• TypeScript definition is updated/provided or not needed
• Changelog is provided or not needed

[codecov]

Codecov Report

Merging #16569 into master will increase coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #16569      +/-   ##
==========================================
+ Coverage   95.71%   95.75%   +0.04%     
==========================================
  Files         258      258              
  Lines        7120     7120              
  Branches     1970     2006      +36     
==========================================
+ Hits         6815     6818       +3     
+ Misses        303      300       -3     
  Partials        2        2

Impacted Files	Coverage Δ
components/_util/wave.tsx	88.67% <0%> (+2.83%)	⬆️

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