fix: adjust vue template sourcemap

[Demivan]

Description

Vue template sourcemaps were off by one line. This fixes Vue template coverage in Vitest.

Fixes vitest-dev/vitest#751

Sourcemap before:

Sourcemap after:

Vitest coverage before:

Vitest coverage after:

Additional context

Code is being concatenated using newlines here:

vite/packages/plugin-vue/src/main.ts

Line 192 in b146007

let resolvedCode = output.join('\n')

So need to adjust sourcemaps by one line too.

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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