remove unnecessary units

[icecream17]

This is extremely minor so I haven't filled in most of the checklist

Changes 0px 0px to 0 0

Using units after 0 causes a lint warning in vscode, css(zeroUnits), and also it's consistent with the omission in margin: 0 0 0.5rem 0

There are some cases in calc where units are required, but this doesn't apply since the change is in drop-shadow

Please don't delete this checklist! Before submitting the PR, please make sure you do the following:

• It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs
• This message body should clearly illustrate what problems it solves.
• Ideally, include a test that fails without this PR but passes with it.

Tests

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• If your PR makes a change that should be noted in one or more packages' changelogs, generate a changeset by running pnpx changeset and following the prompts. All changesets should be patch until SvelteKit 1.0

[changeset-bot]

🦋 Changeset detected

Latest commit: 7b2bd6f

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

This PR includes changesets to release 1 package

Name	Type
create-svelte	Patch

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[Rich-Harris]

thanks!