[bug report] El drawer size attribute source code conflicts with document type

[Ylushen]

Element UI version

2.13.1

OS/Browsers version

win10 chorme 版本 81.0.4044.138（正式版本） （64 位）

Vue version

2.6.11

Reproduction Link

https://jsfiddle.net/mmx38qxw/

Steps to reproduce

文档中有提供Number类型，使用会抛警告

What is Expected?

填Number属性自动转换为px，跟文档一致

What is actually happening?

填Number会抛出类型错误警告，也不会被转换为px

[element-bot]

Translation of this issue:

Element UI version

2.13.1

OS/Browsers version

Win10 chord version 81.0.4044.138 (official version) (64 bit)

Vue version

2.6.11

Reproduction Link

https://jsfiddle.net/mmx38qxw/

Steps to reproduce

Number type is provided in the document, warning will be thrown when using

What is Expected?

Fill in the number attribute and automatically convert it to PX, which is consistent with the document

What is actually happening?

Filling in number will throw a type error warning and will not be converted to PX

[cs1707]

Duplicate of #20636