Remove storage_version column from snippets
What does this MR do?
In !22275 (merged), we added the columns repository_storage and storage_version to the snippet table. Nevertheless, after #39176 (comment 270821384) it seems we don't need storage_version since it's a column needed only for legacy storage and we're only using hashed storage in snippet repositories.
Does this MR meet the acceptance criteria?
Conformity
Edited by Francisco Javier López (ex-Gitlab)