fix: circle bg image in home page

[yutingzhao1991]

💡 Background and solution

之前的图有点问题，修改前：

修改后：

🔗 Related issue link

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Name	Status	Preview	Comments	Updated (UTC)
ant-design-web3	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jun 12, 2024 8:47am

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Latest commit: e0a38e3

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (61c17c5) to head (e0a38e3).

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #962   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          712       712           
  Lines        21624     21624           
  Branches      1225      1225           
=========================================
  Hits         21624     21624           

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