doc(DockView): update dockview sample code

[ArgoZhang]

update dockview sample code

Summary of the changes (Less than 80 chars)

简单描述你更改了什么, 不超过80个字符；如果有关联 Issue 请在下方填写相关编号

Description

fixes #4389

Regression?

• Yes
• No

[If yes, specify the version the behavior has regressed from]

[是否影响老版本]

Risk

• High
• Medium
• Low

[Justify the selection above]

Verification

• Manual (required)
• Automated

Packaging changes reviewed?

• Yes
• No
• N/A

☑️ Self Check before Merge

⚠️ Please check all items below before review. ⚠️

• Doc is updated/provided or not needed
• Demo is updated/provided or not needed
• Merge the latest code from the main branch

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (119e5d7) to head (ce65fc3).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #4390   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          613       613           
  Lines        26580     26580           
  Branches      3875      3875           
=========================================
  Hits         26580     26580           

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