add PageHeader css background

[maiqingqiang]

add page-header css background

🤔 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?)

🔗 Related issue link

💡 Background and solution

上一版本的 PageHeader 是自带白色背景的，更新到 v3.23.1 颜色就没有了。所以把白色背景补回来

📝 Changelog

Language	Changelog
🇺🇸 English	add page-header css background
🇨🇳 Chinese	给 PageHeader 添加背景色

☑️ 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

[netlify]

Deploy preview for ant-design ready!

Built with commit 26f7135

https://deploy-preview-18632--ant-design.netlify.com

[codecov]

Codecov Report

Merging #18632 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #18632   +/-   ##
=======================================
  Coverage   96.74%   96.74%           
=======================================
  Files         281      281           
  Lines        7552     7552           
  Branches     2062     2093   +31     
=======================================
  Hits         7306     7306           
  Misses        244      244           
  Partials        2        2

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[codecov]

Codecov Report

Merging #18632 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #18632   +/-   ##
=======================================
  Coverage   96.74%   96.74%           
=======================================
  Files         281      281           
  Lines        7552     7552           
  Branches     2062     2093   +31     
=======================================
  Hits         7306     7306           
  Misses        244      244           
  Partials        2        2

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update aa9b9db...26f7135. Read the comment docs.

[dengfuping]

• @maiqingqiang 优化后的 PageHeader 不内置背景颜色了，应该由底色决定。

[dengfuping]

• Ref PR: 🔥feat: new pageheader style #18128