fix: Adding ant-upload-btn class to the upload component

[PixelDust22]

This is a ...

• New feature
• Bug fix
• Site / document update
• Component style update
• TypeScript definition update
• Refactoring
• Code style optimization
• Branch merge
• Other (about what?)

What's the background?

It was discovered that when the screen is wider than the upload component content, clicking outside of the content bounding box does not trigger the upload dialog. Dragging a file outside of that box causes the browser to open that file instead of uploading the file.

This bug does not exist on the React version of ant design. After comparing the two versions, it was discovered that the Vue implementation is missing a class on the wrapping span, causing the layout for that wrapper to be broken.

This PR addresses the issue by adding back the missing class name.

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

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[codecov]

Codecov Report

Merging #1742 into master will not change coverage.
The diff coverage is n/a.

@@ Coverage Diff @@ ## master #1742 +/- ## ======================================= Coverage 88.09% 88.09% ======================================= Files 157 157 Lines 5416 5416 Branches 1524 1524 ======================================= Hits 4771 4771 Misses 576 576 Partials 69 69

Impacted Files	Coverage Δ
components/upload/Upload.jsx	84.15% <ø> (ø)	⬆️

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[tangjinzhou]

you should change this line to <VcUpload {...vcUploadProps} class={${prefixCls}-btn}>
https://github.com/vueComponent/ant-design-vue/blob/master/components/upload/Upload.jsx#L276

[PixelDust22]

The requested changes have been made.

[github-actions]

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