docs(trac): Clarify schema.json limit (#1302)

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# [DEVDOCS-] N/A

## What changed?
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* Adds a clarification that the 64 KB size limit for `schema.json` is calculated after the file has been minimized.

## Release notes draft
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language. Don't be too technical. Explain how the change will benefit
the merchant and link to the feature. -->
Clarified that the 64 KB size limit for `schema.json` applies to the minimized file size.

## Anything else?
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N/A

ping {@rtalvarez}

Author: bc-tatiana

docs/storefront/stencil/themes/foundations/customizability.mdx

@@ -96,7 +96,7 @@ To prevent errors upon theme upload and avoid possible loss of customizations ma
 * **Single-instance restriction per storefront.** We strongly recommend opening only one instance of Theme Styles at a time against each storefront. We recommend this because there is currently no synchronization mechanism to reconcile configuration changes made by multiple Theme Styles instances. The `schema.json` file will record the last changes made by any instance, but changes saved earlier by other instances might be lost.
 * **Single-storefront restriction per editor.** In the current release, users can have only one storefront open in Theme Styles at a time. To bypass the cookie that imposes this restriction, a workaround is to open an "Incognito"/private-browsing window on an additional storefront.
 * **File name, location, and structure.** Your theme's `schema.json` file must be named `schema.json`. It must reside in the root of your theme directory and must be valid JSON.
-* **File size.** The maximum size for a `schema.json` file is 64 KB. Exceeding this limit will trigger an error upon uploading the theme to BigCommerce. Apart from this size constraint, there is no limit on the number of keys and values that you can place in a theme's `schema.json`.
+* **File size.** The maximum size for a `schema.json` file is 64 KB. The limit is calculated after the file has been minimized. Exceeding this limit will trigger an error upon uploading the theme to BigCommerce. Apart from this size constraint, there is no limit on the number of keys and values that you can place in a theme's `schema.json`.
 
 ## Managing keys between versions