chore: fix dev build replacing undefined

[sapphi-red]

Description

This bug only happens with pnpm dev.
pnpm dev externalizes dependencies instead of bundling them.

Here we are using the named export: convertSourceMap.mapFileCommentRegex.

vite/packages/vite/src/node/server/transformRequest.ts

Line 5 in ee8c7a6

import * as convertSourceMap from 'convert-source-map'

vite/packages/vite/src/node/server/transformRequest.ts

Line 201 in ee8c7a6

code = code.replace(convertSourceMap.mapFileCommentRegex, blankReplacer)

But because convert-source-map uses a uncommon notation, Node.js fails to detect this named export.
As a result, in build, rollup achieves to handle this, and in dev, convertSourceMap.mapFileCommentRegex becomes undefined.
https://github.com/thlorenz/convert-source-map/blob/46c2b78aa56d25a77d3ea237051aeb5d9e7f750c/index.js#L11-L16

Then this line will be .replace(undefined, blankReplacer) and breaks @vite/client.

Additional context

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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