fix : reactivity bug with single script in svelte:head #13378

[adiguba]

template_with_script() is buggy when it contains only one <script> element, because the run_scripts() will clone and replace the scripts.

There no problem when using a DocumentFragment because they are replaced immediately.
But with a single node the element is replaced later with queue_micro_task().

=> So the cloned script is put on the DOM, but template_with_script() will return the previous script (so reactivity is broken).

See #13378

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[adiguba]

Oops didn't see that I was not on the last.
Will close this PR and create another...