chore: fix compiler-errors test suite

[Rich-Harris]

Bit of an oversight — there's a bunch of tests in compiler-errors that aren't actually doing anything, because the files are called input.svelte instead of main.svelte.

Fixes #9765

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🦋 Changeset detected

Latest commit: 3ef9987

The changes in this PR will be included in the next version bump.

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[dummdidumm]

I'll take this, thanks for noticing that