fix: the color of Content should change in darkmode

[nova1751]

[中文版模板 / Chinese template]

🤔 This is a ...

• New feature
• Bug fix
• Site / documentation update
• Demo update
• Component style update
• TypeScript definition update
• Bundle size optimization
• Performance optimization
• Enhancement feature
• Internationalization
• Refactoring
• Code style optimization
• Test Case
• Branch merge
• Workflow
• Other (about what?)

🔗 Related issue link

#47434

💡 Background and solution

The color of Content component of Layout stay the same when theme changes.Adding a color rule can solve this problem.

📝 Changelog

Language	Changelog
🇺🇸 English	Fix the font color of Content not change in darkmode
🇨🇳 Chinese	修复Content元素中的字体颜色在暗黑模式下不改变的问题

☑️ Self-Check before Merge

⚠️ Please check all items below before requesting a reviewing. ⚠️

• 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

[stackblitz]

Run & review this pull request in StackBlitz Codeflow.

[github-actions]

👁 Visual Regression Report for PR #47441 Failed ❌

🎯 Target branch: master (e6b756a)
📖 View Full Report ↗︎

Image name	Expected	Actual	Diff
layout-component-token.dark.png
layout-component-token.dark.css-var.png
layout-custom-trigger-debug.dark.png
layout-custom-trigger-debug.dark.css-var.png
layout-custom-trigger.dark.png
layout-custom-trigger.dark.css-var.png
layout-fixed.dark.png
layout-fixed.dark.css-var.png
layout-responsive.dark.png
layout-responsive.dark.css-var.png

Check Full Report for details

[github-actions]

[codesandbox-ci]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (e6b756a) 100.00% compared to head (6c1700c) 100.00%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master    #47441   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          734       734           
  Lines        12593     12593           
  Branches      3298      3298           
=========================================
  Hits         12593     12593           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[github-actions]

🎉 Thank you for your contribution! If you have not yet joined our DingTalk community group, please feel free to join us (when joining, please provide the link to this PR).

🎉 感谢您的贡献！如果您还没有加入钉钉社区群，请扫描下方二维码加入我们（加群时请提供此 PR 链接）。