Update Space-0 Token To Have a Unit (#9904)

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### WHY are these changes introduced?

Using a unitless value (aka `0`) inside of a `calc` causes `calc` to
error, thus breaking the CSS rule you are trying to use. Here, I am
adding a unit to the value to fix this problem. Per [this design tokens
format
module](https://design-tokens.github.io/community-group/format/#dimension),
values should include units, including 0.

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-->

### WHAT is this pull request doing?

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This is allowing for the `space-0` token to be used inside of a `calc`.

### How to 🎩

🖥 [Local development
instructions](https://github.com/Shopify/polaris/blob/main/README.md#local-development)
🗒 [General tophatting
guidelines](https://github.com/Shopify/polaris/blob/main/documentation/Tophatting.md)
📄 [Changelog
guidelines](https://github.com/Shopify/polaris/blob/main/.github/CONTRIBUTING.md#changelog)

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  Give as much information as needed to experiment with the component
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I built the tokens package and saw the correct value was outputted in
the build file.

```
--p-space-0:0rem;
```

Documentation is updated

<img width="1374" alt="image"
src="https://github.com/Shopify/polaris/assets/3689812/e251151d-cf8d-416b-92d8-e7501e0a7783">


### 🎩 checklist

- [ ] Tested on
[mobile](https://github.com/Shopify/polaris/blob/main/documentation/Tophatting.md#cross-browser-testing)
- [ ] Tested on [multiple
browsers](https://help.shopify.com/en/manual/shopify-admin/supported-browsers)
- [ ] Tested for
[accessibility](https://github.com/Shopify/polaris/blob/main/documentation/Accessibility%20testing.md)
- [ ] Updated the component's `README.md` with documentation changes
- [ ] [Tophatted
documentation](https://github.com/Shopify/polaris/blob/main/documentation/Tophatting%20documentation.md)
changes in the style guide

---------

Co-authored-by: Aaron Casanova <[email protected]>

.changeset/clever-sheep-sip.md

@@ -0,0 +1,5 @@
+---
+'@shopify/polaris-tokens': patch
+---
+
+Added a unit to the `space-0` token

polaris-tokens/src/token-groups/space.ts

@@ -32,7 +32,7 @@ export const space: {
   [TokenName in SpaceTokenName]: MetadataProperties;
 } = {
   'space-0': {
-    value: '0',
+    value: '0px',
   },
   'space-025': {
     value: '1px',