Gallery block: turn on auto-migration of v1 Gallery blocks to v2 format when edited#4315

mkevins merged 3 commits intodevelopwordpress-mobile/gutenberg-mobile:developfrom

update/gallery-block-disable-v2-when-useBalanceTags-setwordpress-mobile/gutenberg-mobile:update/gallery-block-disable-v2-when-useBalanceTags-setCopy head branch name to clipboard