Fix custom component reload mode

[freddyaboulton]

Description

The problem was that the custom component was only being mounted once so prop updates were not being propagated down to the component. So my fix was to modify the $effect in MountCustomComponent. Also, instead of using onDestroy, I am returning a function from $effect to do the cleanup.

Closes: #12965

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🦄 change detected

This Pull Request includes changes to the following packages.

Package	Version
@gradio/core	patch
gradio	patch

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• Fix custom component reload mode

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✅ Changeset approved by @freddyaboulton

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[pngwn]

uuuuumount

[pngwn]

This looks great. Thanks for the clean fix @freddyaboulton!