Related to #36169
this PR makes `gc-lfs` update the `repo.LFSSize` on object removal,
updates the test to also cover the recalculation of sizes.
doesn't touch `storage-lfs` as it removes files with no LFSMetaObject
row, and LFSSize is calculated from those rows
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Signed-off-by: Myle <myle.ataraxia@pm.me>
Co-authored-by: silverwind <me@silverwind.io>