fix remote docs example

[hichemfantar]

Why:

Closes: #4116

What's being changed (if available, include any code snippets, screenshots, or gifs):

Update page routing to accommodate an optional slug parameter, ensuring proper handling when the slug is not provided.

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• I have reviewed my changes in staging, available via the View
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Latest commit: 5ae7b03

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[hichemfantar]

@dimaMachina the fix works and is the same as v3 except it uses empty string instead of 'index'

letting you know so you're aware in case it's not intended

nextra/examples/swr-site/pages/en/remote/graphql-yoga/[[...slug]].mdx

Line 7 in d91e2d5

const path = params.slug?.join('/') ?? 'index'

[dimaMachina]

Thanks for fixing it, it's strange that the build command doesn't fail