Default theme.json: The definition of `styles.elements.button.spacing.padding` is incorrect

[t-hamano]

What problem does this address?

For styles.elements.button.spacing.padding in theme.json, only objects with fields top, right, bottom, and left are allowed. However, the default theme.json specifies a string. Therefore, the code editor reports this field as an error.

What is your proposed solution?

It actually seems to work correctly with a string, but I think one of the following improvements is needed.

• Rewrite to object in default theme.json
• If the specification is expected to accept a string, update the JSON schema

[ramonjd]

Upcoming fix for this already in https://github.com/WordPress/gutenberg/pull/57374/files#diff-ba57fd27dc15a6079df31427f442f760cbe4035a941cfb1a4763c7cf90766b15R300