Params in object are now parsed as json instead of query param keys

[Ken-vdE]

Environment

node 22
nuxt 3.15.4

Reproduction

See 0d84f7b#diff-39b2554fd18da165b59a6351b1aafff3714e2a80c1435f2de9706355b4d32351L72

Run this:

$fetch('some-url', {
    baseURL: "http://some-domain.test",
    params: {
        filter: {
            site: undefined,
            "url:is": "something"
        }
    }
})

Describe the bug

See 0d84f7b#diff-39b2554fd18da165b59a6351b1aafff3714e2a80c1435f2de9706355b4d32351L72

The URL is then parsed into some-url?filter=%7B%22url:is%22:%22something%22%7D (some-url?filter={"url:is":"something"})
and it previously was correct: some-url?filter%5Burl:is%5D=something (some-url?filter[url:is]=something)

Additional context

No response

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