[Svelte 5] No more "Attributes need to be unique" error on duplicate class:name and style:property directives

[adiguba]

Describe the bug

I don't know if it's intentional or not, but there is no longer an error message in case of duplicate directives for class:name and style:property.

Ex:

<button
	style:border={border}
	style:border="1px solid red"
>
	button
</button>

On Svelte 4, this code will produce a compile error "Attributes need to be unique".
This is no longer the case with Svelte 5, (runes enabled or not)

Reproduction

Svelte 4 (OK) : https://svelte.dev/repl/09eaa85fa6b842959418bbcc9c0d1cf2?version=4.2.19

Svelte 5, non-runes mode : https://svelte-5-preview.vercel.app/#H4sIAAAAAAAACnVQwWrDMAz9FaFLoQzCrm5c6HfMO6SxOgxObCRlpA3598Y1pbBRdJCe9HhP0oKXEEnQfC04dgOhwVPO-IF6zQXIL0WlDUuauC-dVnoOWY9udEpzTqwQSUHCjQ7Q7GEgH6YBEkPs-Idg3_xhnhN74oMb2-YltUV7nlRTKbWPnYipSnYp0tbaXcW79T3j4VgJotdIpnrZpeb_A4efeQZJMXhg8g4L43Hac5m2qdVx-8GQfLgE8miUJ1q_1ztxzxAlPgEAAA==

Svelte 5, runes mode : https://svelte-5-preview.vercel.app/#H4sIAAAAAAAACnVPywrCMBD8lbAIKgjFa2wEv8N4aJutBNImZLeihv67jUE8iOxhZ2ZnXwl665BAnhOMzYAg4RQC7IAfIRO6oWNcOPkpdlmpqYs28FGPmh2ySBloJvvEnWh9NBizMgslViH6QJvtQY919W1bom4nZp8hd64hkgMaOw0q5TFKqXXh6_m_wzXxisVA_HAoy26VSv4taNiHuyDvrBERjYbseL_xOaauCjou_w7e2N6iAclxwvkyvwAgiWkEKgEAAA==

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