Gallery Block Spacing not apply to the page

Problem/Motivation

Gallery Block spacing shows on the edit page but is not being applied to the page. It does not generate a variable style or styling controlling block spacing within the Gallery template. While the block spacing works correctly for paragraphs and other templates, it currently does not affect the Gallery.

Steps to reproduce

Add the custom style to the `THEMENAME.gutenberg.yml` file. Enable `spacingSizes` and set `blockGap` to true. Then, insert a Gallery onto the page, configure the block spacing as needed, and save the page.

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes