fix: make htmlFallback more permissive

[sapphi-red]

Description

I only tested the fix in #15025 by fetch('/'). But fetch('/') was sending Accept: */*. 🤦

Also it turns out that wait-on sends Accept: application/json, text/plain, */*. We need to remove the json part.

fixes #15022

Additional context

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines, especially the Pull Request Guidelines.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Update the corresponding documentation if needed.
• Ideally, include relevant tests that fail without this PR but pass with it.

[sapphi-red]

/ecosystem-ci run

[patak-dev]

@bluwy was also fine removing this check, so let's go with it. Thanks for re-checking the repro and the quick fix Sapphi!

[vite-ecosystem-ci]

📝 Ran ecosystem CI on 2847753: Open

suite	result	latest scheduled
analogjs	✅ success	✅ success
astro	✅ success	✅ success
histoire	❌ failure	❌ failure
ladle	✅ success	✅ success
laravel	❌ failure	❌ failure
marko	✅ success	✅ success
nuxt	✅ success	✅ success
nx	❌ failure	❌ failure
previewjs	✅ success	✅ success
qwik	❌ failure	❌ failure
rakkas	✅ success	✅ success
sveltekit	❌ failure	❌ failure
unocss	✅ success	✅ success
vike	✅ success	✅ success
vite-plugin-pwa	✅ success	✅ success
vite-plugin-react	✅ success	✅ success
vite-plugin-react-pages	✅ success	✅ success
vite-plugin-react-swc	✅ success	✅ success
vite-plugin-svelte	✅ success	✅ success
vite-plugin-vue	✅ success	✅ success
vite-setup-catalogue	✅ success	✅ success
vitepress	✅ success	✅ success
vitest	✅ success	✅ success