chore: removed deprecated config.package type

[GauBen]

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Support for config.package was removed in #8922 (10 month ago) but the type declaration survived the svelte-kit v2 major version. I guess it should be removed now, as I tried using it (encouraged by the type declaration) and failed with this message

> config.package is no longer supported. See https://github.com/sveltejs/kit/discussions/8825 for more information.
    at load_config (file:///@sveltejs/package/src/config.js:21:9)
    at async file:///@sveltejs/package/src/cli.js:29:19

It may be time to remove this message too, it can be found here:

https://github.com/sveltejs/kit/blame/main/packages/package/src/config.js#L20-L24

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Latest commit: e142eb7

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[dummdidumm]

Thank you!

[GauBen]

You're welcome!

Should we remove these lines too?

kit/packages/package/src/config.js

Lines 20 to 24 in 31512a9

	if (config.package) {
	throw new Error(
	'config.package is no longer supported. See https://github.com/sveltejs/kit/discussions/8825 for more information.'
	);
	}

[dummdidumm]

No, we should do this in @sveltejs/package version 3 (so that people upgrading from 1 to 2 get a good error message)