Fix sizeSlug does not update in Gallery block

[mkevins]

Related PR:

gutenberg: WordPress/gutenberg#27691

To test (test on web and mobile):

• Create a new post
• Add a gallery block
• Add a few images
• Tap block settings
• Change image size setting (try "Medium")

Expect the size setting to be reflected after selecting the option.

PR submission checklist:

• I have considered adding unit tests where possible.
• I have considered if this change warrants user-facing release notes more info and have added them to RELEASE-NOTES.txt if necessary.

[peril-wordpress-mobile]

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[antonis]

The code change in the linked Gutenberg PR LGTM and behaves as expected 👍

ps. I've run npm install and pushed an update in the package-lock.json hopping to fix the failed Check Correctness. This didn't work 🤷 (reverted)
I then noticed that this fails in most open PRs at this point and should be a CI issue.

[enejb]

Thanks for working on this. I found this issue (#2880) when I was doing the santy testing. It seems to be the same issue.

[mkevins]

Thanks for taking the time to review Antonis, and Enej for linking to the related issue. And thanks @Lovor01 for the fix!