fix(time-picker): fix issue with read-only mode still being editable

[oljc]

Types of changes

• New feature
• Bug fix
• Enhancement
• Component style change
• Typescript definition change
• Documentation change
• Coding style change
• Refactoring
• Test cases
• Continuous integration
• Breaking change
• Others

Background and context

readonly 不生效，只读模式点击输入框依然可以进行修改。

Solution

How is the change tested?

Changelog

Type	Component	Changelog(CN)	Changelog(EN)	Related issues
fix	time-picker	修复只读模式仍可编辑问题	Fix issue with read-only mode still being editable	Closed #3151
docs	time-picker	补充 placeholder 类型定义	Added placeholder type definition

Checklist:

• Test suite passes (npm run test)
• Provide changelog for relevant changes (e.g. bug fixes and new features) if applicable.
• Changes are submitted to the appropriate branch (e.g. features should be submitted to feature branch and others
  should be submitted to main branch)

Other information

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