fix: preserve this when invoking standard validator

[thes01]

The validate function call currently loses the dynamic this binding. Thus, if a standard validator's validate function is a class method that makes use of this, it will be undefined. I stumbled upon this when using TypeBox's standard schema adapter.

This PR inlines the validate call so that the dynamic context isn't lost.

Not sure if a test is necessary, since this is somewhat a niche use case.

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🦋 Changeset detected

Latest commit: c1158ec

The changes in this PR will be included in the next version bump.

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@sveltejs/kit	Patch

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[dummdidumm]

thank you!